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This is to certify that the

thesis entitled

PRIMARY PRODUCTIVITY AND ENERGY
RELATIONSHIPS IN ARTIFICIAL STREAMS

presented by

Niles R. Kevern

has been accepted towards fulfillment
of the requirements for

Ph. D. degree inFisheries & Wildlife

 

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Major professor

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ABSTRACT

PRIMARY PRODUCTIVITY AND ENERGY RELATIONSHIPS
IN ARTIFICIAL STREAMS

by Niles R. Kevern

The productivity and energetics of algal communities in two,
recirculating, artificial streams were investigated. Emphases were
placed on a comparative study of methods used to measure primary
productivity in flowing waters and on the effects of controlled environ—
mental characteristics on energy flow.

The artificial streams, with incandescent lights as the source of
energy, were established with distilled water and inorganic nutrients
and were seeded with algae from a local stream. Succession ended

with a filamentous blue-green alga, Plectonema Boryanum Gomont, as

 

the dominant organism. Productivity of the algae was measured by
pH-carbon dioxide changes, upstream-downstream oxygen changes,
and by the biomass of periphyton collected on artificial substrates.
Increases in light intensity, current velocity, and chelate concen-
trations caused significant increases in productivity. An increase in
temperature resulted in a Q10 of 1.4 for the growth rate of the algae
indicating that respiration increased about the same as photosynthesis
and causing only a slight increase in net productivity. Alteration of the
photoperiod did not cause a significant increase in productivity.
Productivity measured by the biomass of periphyton collected on
substrates was generally lower than estimates by the carbon dioxide

and oxygen methods, but substrate estimates increased when calculations

Niles R. Kevern

were based on the growth rate occurring on the last few days of an ex-
tended exposure period. The growth of the periphyton population was
described as having a J-shaped form. A close linear relationship was
noted between the concentration of phytopigment, extracted by ethanol,
and the ash-free dry weight of the periphyton.

‘Estimates of net productivity by the carbon dioxide and oxygen
methods were in general agreement when the oxygen values were cor-
rected by a photosynthetic quotient of l. l to l. 3 depending upon the
measured caloric value of the algae.

The radiant energy received by the periphyton was about 1% of the
average daylight intensity. rRadiant energy fixed as the chemical energy
of organic matter varied from 0. 06 to O. 20 g cal cm'?‘ day'1 being some-
what less than the rates of most natural communities. Photosynthetic
efficiencies based on gross productivity varied from 2. l to 12. 5%, while
those based on net productivity varied from O. 9 to 4. 1%... These relatively
high efficiencies were explained on the basis of the predominance of red
wavelengths in the light received by the periphyton and the low light
intensities. High efficiencies generally occurred with high productivities;
however, and increase in productivity caused by an increase in light
intensity was accompanied by a decrease in efficiency.

The primary source of nutrients during the study periods was from
decomposition of periphyton. Phosphorus regeneration was shown to
take place readily in the dark of the reservoirs and filters. Phosphorus
release from insoluble sources occurred when a chelate, EDTA, was
added to the streams and phosphorus was precipitated when suspensions

of kaolin were added to the streams under acid conditions.

PRIMARY PRODUCTIVITY AND ENERGY RELATIONSHIPS
IN ARTIFICIALSTREAMS

BY

Nile s R?- Kevern

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Fisheries and Wildlife

1962

.r’,

'l
6‘.

u.“ I

i .4’ .~_

4:70"?

ACKNOWLEDGMENTS

I offer my sincere thanks to Dr. Robert C. Ball for his super-
vision of the study, for his guidance as my advisor, and for his
unselfish contribution of time.

I wish to thank Drs. Philip J. Clark, Gerald W. Prescott, and
Peter I. Tack for their time given as members of my guidance com-
mittee. .I also thank Dr. Prescott for his aid in taxonomic problems
and Dr. Clark for his advice on presentation of statistical analyses.

-My appreciation is extended to many of my fellow graduate
students for their discussions, opinions, and suggestions relating to
the study.

And to my wife, Kay, I give my thanks for her patience and
understanding through the period of graduate study.

I am also grateful for financial assistance under Fellowship
No. GF-lZ, 649 from the Division of General Medical Sciences of the

National Institutes of Health, Department of Health, Education, and
Welfare.

>{< >:< >1: >:< >:< >:< >1: >:< >:< >:< >:< >:< >:< >:<

ii

TA BLE OF CONTENTS

Page

INTRODUCTION . . . . . . . . ................. 1
LITERATURE REVIEW .................... . 3
pH, Carbon Dioxide, and Alkalinity ............ 4
Oxygen ....... . ................. 7
Artificial Substrates and Pigments ............ 8

C14 and other Methods ................. . . 1 1
Stream Studies ...................... . 12
Related Topics and Reviews ............... . 14

METHODSANDEQUIPMENT.................. l6

Artificial Streams . . . . . . . . . . .......... . 16
Nutrient Medium . . . ................ . . . 19
"Light ................ . . . ..... . . . . 21
Water Temperature .................... 25
Water Velocity and Discharge ...... . . . . . . . . . 26
Specific Conductivity and Total Solids. . ..... . . . . 26
Alkalinity, pH, and Carbon Dioxide. . . ......... Z7
Phosphorus . ..... . . . . . . ........... . 27
'Nitrogen. . . ........ . . . . . . . . . . . . . . . 28
Calorimetry . . ........ . . . . . . . . . ..... 29
Weights ........... . . . . . . ......... 29
Primary Productivity ................... 29

Diurnal ”Oxygen Curves . . . . . . ...... . . . 3O

Diurnal pH-Carbon Dioxide Curves. . . ...... 31

Periphyton Growth andPigment Extraction . . . . 38

STANDARD CONDITIONS AND STUDY PROCEDURES . . . . . 43

RESULTS AND DISCUSSION ..... . ............. 53
Effects of Study Conditions . . . . .......... . . 53
Temperature .................. . . 53
Photoperiod ...... . . . . . . ....... . . 54

iii

TABLE OF CONTENTS - Continued

Page

Light Intensity ................. . . . 60

Current Velocity ................... 63

Chelate ........................ 67

Primary Productivity .............. . . . . . 75
Growth Rates on Artificial Substrates ........ 75

Diurnal Gas Changes ................. 88
Phytopigment Concentration ............. 94

Energy Transfer and Efficiencies ............. 98
Nutrient Observations ..... . ............. 108
Concluding Remarks ................. . . . 116
SUMMARY . ........................ . . . 118
LITERATURE CITED ...................... 120

iv

TA BLE

10.

11.

12.

LIST OF TA BLES

Page
The composition of initial nutrient medium in milli-
grams per liter added to each stream in July, 1959. 20
The concentration of elements in milligrams per'liter
added to each stream on-May 24,. July 21, and October
7,1960......... ..... .21
Absorption of light in artificial streams . . . . 25

Production rate of oxygen in stream No. 2 as calculated
from measurements taken on June 28, 1960 during the
temperature study. . . . . . ............

Standard and study conditions in the artificial streams .

Analysis of variance of production in dry weight at the
five stations of streams 1 and 2.

Comparison of net productivity in g m"2 clay'l organic
weight as measured by the oxygen, carbon dioxide, and
substrate methods. .

Energy transfer and efficiencies for periphyton in
streamslandZ. . . . . . . . . . . ........

Comparisons of primary productivity and efficiencies
for various ecosystems . . . . . . . . . . . . . .

The phosphorus and nitrogen composition and N/P
quotients for the organic weight of periphyton from the
artificial streams. . . . . . . . . . . . .....

Phosphorus regeneration from decomposition of algae
placedin 100 ml water and stored in the dark at 25 C .

Removal of phosphorus from solution by the addition of
100 mg liter"1 kaolin to each artificial stream .

34

44

65

92

100

105

113

115

117

‘FIGURE

1.

2.

10.

11.

LIST OF FIGURES

Page
Diagram of artificial streams. . ......... 17
Conversion of exposure meter readings to energy
units 0 O O O O O O O O O O O O O O I O O O ...... 23

Rate of oxygen production in stream No. 2 during the
temperature study, on June 28, 1960, as estimated by
the area under the curve method . . . . . . . . .

Titration curves of stream water for conversion of
change in pH units to moles of carbon dioxide. .

Diurnal carbon dioxide curve prepared from pH
measurements in stream No. 2 during the temperature
study on July 5, 1960 . . . . . .

Specific conductivity and total alkalinity throughout
the study period .

Available nitrogen and total phosphorus throughout
the study period .

Absorbancy spectrum of 95% ethanol extract of
Plectonema Boryanum Gomont . .

 

The effect of temperature on net production in artis-
ficial streams as measured by carbon dioxide, oxygen,
and substrates.

The effect of photoperiod on net production in artificial
streams as measured by carbon dioxide, oxygen, and
substrates.

The effect of light intensity on net production in arti-

ficial streams as measured by carbon dioxide, oxygen,
and substrates

vi

32

35

39

45

47

51

55

58

61

LIST OF FIGURES - Continued

FIGURE

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

Page
The effect of current velocity on net production in
artificial- streams as measured by carbon dioxide,
oxygen, and substrates ...... . ....... . . . 68

Action of a chelate on orthophosphate concentration in
artificial streams . ............ . . . . . . . 71

The effect of a chelate on net productivity in artificial
streams as measured by carbon dioxide, oxygen, and
substrates ........ ..... 73

Biomass of periphyton on substrates exposed for
various time periods in the artificial streams ..... 78

Growth phases of periphyton on substrates exposed in
artificial streams ...... . ...... . . . . . . . 80

Rate of periphyton growth on substrates in stream 1
during current velocity study . ..... . . . . . . . 82

Rate of periphyton growth on substrates in stream 2
during current velocity study . ......... . . . 84

Energy flow in the artificial streams based on the
mean values of both streams in gram-calories meter
day-1 ........ ..... ...103

-2

Comparison of the daylight and incandescent spectra
with the wavelengths absorbed by phytopigment
extracts.. ......... ..............106

Relationship between nitrogen and phosphorus fixa-
tion by periphyton and periphyton growth . . . . . . . 110

vii

INTRODUC TION

Primary productivity, the fundamental problem of aquatic biology,
is defined by Frey (1956) as radiant energy fixed by photosynthetic
plants as chemical energy. This phenomenon has been the subject of
extensive study for many years with most attention being centered on
lakes and ponds. Primary productivity in flowing waters has received
comparable attention only in recent years with many of the methods
used to measure production in lakes being found inadequate for stream
studies. Development of new methods and techniques for free water
was necessary, since the basic difference between lakes and streams
is the unidirectional flow of water in streams. These free water methods,
that is, methods not requiring isolation of the water mass, are still in
a state of development and refinement.

rLaboratory experiments employing culture vessels, the Warburg
apparatus, and other such tools have contributed significantly to the
methodology used in lake studies and to the understanding of phenomena
relating to primary productivity in standing waters. Comparable
laboratory studies relating to stream productivity, such as the study of
a stream microcosm by Odum and Hoskin (1957), have been few. The
potential then, remains considerable for the use of artificial streams to
investigate the relationships involved in the primary productivity of
flowing waters. Many of these relationships of productivity are based
on the effects of environmental factors on the metabolism of the pro-
ducers. It is possible, in a laboratory situation, to isolate or control
many of the environmental factors in order to determine their influence

on the fixation of energy by autotrophic organisms.

This study of primary productivity in artificial streams was
established with three main objectives, 1) to determine the effects of
certain environmental factors on productivity, 2) to critically compare
and investigate the methods of measuring primary productivity in flow-
ing waters, and 3) to characterize the artificial stream as a research
tool for adding to our knowledge of stream ecology.

Environmental factors were controlled and investigated individually
with the influence on productivity being measured comparatively by the
several methods also under investigation. It was thus possible to evaluate
both the environmental effects and the methods. Since productivity
studies are best quantified in energy terms, the results of the environ-
mental studies were converted to energy flow and efficiencies and these,
in addition to nutrient observations, used to characterize the artificial

streams in comparisons with other aquatic ecosystems.

LITERATURE REVIEW

This review is intended to cover the studies in limnology that
have dealt with primary production in general and with stream studies
in particular.

-Early work, from the middle nineteenth century into the first of
the twentieth century, was predominantly European and dealt for the
most part with plankton studies in lakes. Welch (1951) gives a historical
review of limnology and mentions such early European investigators
as J. Miiller,rP. E. Miiller, A. Fritsch, F. A. Forel, and F. Simony.
Early work in the UnitedStates was likewise dominated by studies con-
cerned with plankton in lakes, largely zooplankton as evidenced in the
five year review of Ward (1899) and the Work of Marsh (1899). Wolle in
1887 published the first notable key to the algae of the United States,
but made little mention of limnological relationships. Early United
States literature was not without some indication of the studies of pro-
duction and aquatic ecology which were to follow. S. A. Forbes (1887)
gave limnology in the United States much of its ecological bearing and
Marsh (1899) mentioned measurement of productiveness as a future
need.

During the first part of the 1900's, production studies were
numerous enough to prompt several philosophical papers attempting
to define, justify, and clarify production and the measurement of pro—
duction. Transeau (1926) expressed concern over the exhaustion of
our stored energy supply and made one of the first estimations of energy
fixation by plants. ‘Klugh in 1926 stated the ultimate aim of limnology
to be fish production and attempted to infer a productivity index for

lakes based upon the rooted aquatic vegetation. Strdm in 1928 spoke of

' "production biology" as the biological build-up of organic matter by
autotrophic plants, primarily algae, with the final practical aim being
fish production. Strgim (pp: 925.“) based his discussion on the work of
many early and well-known investigators such as Naumann, Thienemann,
Wesenberg-Lund, Alm, Alsterberg, Uterm'dhl, Birge and Juday,-Atkins,
and Harvey. Thienemann in 1931 tried to reconcile the many interpre-
tations of production already existing by that time. In the United States,
Viosca‘(1935) published an essay on the dependence of fish production

upon productivity at lower trophic levels.

pH, Carbon Dioxide, and Alkalinity

The general relationship of carbon dioxide and oxygen with photo—
synthesis has been known since the observations of J- Priestly in the
eighteenth century, but it was not until the twentieth century that this
relationship was applied significantly in the measurement of primary
productivity.

In 1914, Birge and Juday discussed factors involved in producing
a stratum of strongly alkaline water. This happened in lakes when a
thermocline occurred near the surface thus concentrating photosynthetic
organisms which, under favorable conditions, caused a drop in free and
half-boundcarbon dioxide. -No attempt was made to calculate pro-
duction by this rise of alkalinity. Moore and his colleagues in 1915
noted a marked rise in the pH and alkalinity of sea water caused by
photosynthesis and were the first to relate pH changes to carbon dioxide
changes in order to measure production of dry organic matter in the
sea. Osterhout and Haas (1918a) found the amount of carbon dioxide
abstracted by marine algae was a linear function of pH in‘the range
studied by them (pH 8. 1 to 8. 3). Osterhout and Haas (2p; c_i_t_.) concluded

that the amount of photosynthesis could be measured by the}. change of pH

values. -Moore, Whitley, and Webster in 1921 stated that as the supply
of carbon is drawn from dissolved bicarbonates, the reaction of the
medium becomes more alkaline and the increase can be used to measure
photosynthetic activity. The limit was determined to be when all of

the bicarbonate was converted to carbonates at about pH 9. 1. ‘After this,
free hydroxide ions were formed and the rapid increase in the alkali
killed the algae. Schutow (1926) observed that the pH fluctuated when the
carbon dioxide of bicarbonate was used up. Saunders in 1926 discussed
the dependence of pH on the concentration of carbonate, bicarbonate,

and carbon dioxide and on the temperature and neutral salts. Atkins
(1926a, b) also discussed temperature, saying that an increase lessens
the solubility of carbon dioxide and that a correction was necessary
before alkalinity changes could be used for photosynthetic measurements.
Atkins (pp; 333:) observed annual changes of pH from 7. 6 in winter to

9. 3 in summer in a fresh-water reservoir and noted that ranges should
be greater in fresh-water than in the more highly buffered salt-water.
Atkins' method of using pH changes to measure carbon dioxide assimi-
lated by photosynthesis depended upon correlating pH changes by adding

. 01 N acid with pH changes produced by an equivalent amount of carbon
dioxide.

Diurnal pH changes of 7. 4 to 9. 6 in a Minnesota lake led Philip
(1927) to caution investigators against using one pH determination as
representative for any natural water. Such large diurnal pH changes
might well have encouraged biologists to use this method to measure
photosynthesis; however, some other reports gave the opposite im-
pression. In some northeastern lakes of Wisconsin, the maximum
diurnal variation was found to be 0. 5 pH unit and these lakes ranged,
in carbon dioxide of all forms, from 1. 0 mg /1 to 7. 50 mg/l (Juday,

e_t a_l. , '1935). Baumberger and Winzler (1939), using glass electrodes

with a sensitivity of 0. 02 pH unit, claimed they could measure carbon
dioxide changes with a sensitivity of 2.. 3 percent.

-Little mention had been made concerning diffusion corrections
until Osterlind‘ (1947) remarked that it was difficult to measure growth
at a‘pH higher than 8. 2 because of carbon dioxide absorption from the
air. .Osterlind (gp. c_:i_t.) measured carbon dioxide consumption by pH
allowing for alkalinity changes. Ruttner (1948) used conductivity to
measure carbon dioxide, employing conversion graphs made by blowing
expired air (carbon dioxide) through the medium and graphing the
conductivity changes. This same procedure was used later by Verduin
(1960) to make pH-carbon dioxide conversion graphs. Verduin (1951,
1956) outlined, in detail, the procedures necessary to use pH changes
tomeasure photosynthetic rates. Verduin (op. cit.) claimed that with
modern pH meters, the error involved in measuring carbon dioxide
is less than 10 percent even when the pH change is as low as O. 3 pH
unit and also that in most cases diffusion was negligible. (Ryther (1956)
pointed out that the uptake of carbon dioxide was the most direct
measure of photosynthesis since the carbon dioxide was equivalent,
mole for mole, to organic carbon. Ryther (pp. gi_t.) also stated that
the only practical method of following changes in the entire buffer
system of an aquatic environment was by pH, but that pH was probably
the least sensitive of modern methods.

Recently several authors have been concerned with the proper
methods to be used in construction of the pH-carbon dioxide conversion
graph. Proper interpretation of the pH-carbon dioxide relationship is
necessary for accurate productivity estimates and these recent reports
have helped to improve the pH method. Further discussion of these

reports is taken up under the section on methods.

Oxygen

Although oxygen is the counterpart of carbon dioxide in the photo-
synthetic process, oxygen measurements apparently did not receive
as much early attention as did pH and carbon dioxide as a method for
measuring production. Scott in 1924 studied the diurnal oxygen pulse
in a lake, observing definite pulses during clear, calm weather.

Scott (pp. cit.) noted the oxygen increase to be caused by photosynthesis
and absorption and only to photosynthesis after saturation was reached.
One of the greatest contributions to the methodology of production
biology and to the use of oxygen measurements was the development

of the light and dark (L-D) bottle method by Gaarder and Gran (1927).
Since that time the L-D bottle method has been used to measure pro-
ductivity probably more than any other method. Among the first to use
the L-D bottle method were Marshall and Orr (1928) who measured

the oxygen evolved by diatom cultures in bottles suspended at various
depths in the sea.

The L—D bottle method has been subjected to much detailed study
in recent years probably as a result of a descrepancy reported
occasionally in which the oxygen content of the dark bottle is greater
than that of the light bottle. One criticism of the L-D bottle method is
that it isolates the photosynthetic organisms from the environment and
this point is important in stream studies. Also the L-D bottle method
is not useful to measure production by benthic algae and higher aquatic
plants. The simplicity and adaptability of the L-D bottle method which
gave it much of its popularity may also have deterred development of
oxygen methods for use in free-water.

Many investigators, not always interested in productivity,
measured the oxygen content of water samples taken from the environ-

ment at various time intervals. Wiebe in 1930, working with a fish pond

containing a bloom of Anabaena, found an increase in oxygen of 4. 68

mg liter‘l to 15.9 mg liter‘1 from 6:00 AM to 3:00 PM. Wiebe ($1. c_i_t_.)
reported that the oxygen increase in the ponds was roughly proportional
to the amount of algae present. Olson (1932) made hourly oxygen
measurements in a lake and had data which would have made an
excellent diurnal oxygen curve; however, he was only interested in
shoWing the availability of oxygen for fish. Stephenson, Zoond, and
Eyre (1934), although they did not use oxygen to measure productivity,
did compare the oxygen increases between autotrophic and heterotrophic
communities and found that oxygen increases were much greater in the
autotrophic c ommunitie s .

- The use of a dropping mercury electrode to produce a continuous
oxygen record was reported by Juday, Blair, and Wilda in 1943 thus
marking one of the first attempts to place production measurements on
a semi-automatic basis. The continuous monitoring of dissolved oxygen
by instruments has received considerable attention and development in
the past few years. The use of diurnal oxygen measurements as a
popular method was greatly advanced when Odum (1956) published, in
detail, the procedures for the method as used by him in measuring the
productivity of springs in Florida. Free—water gas curves, 1. e. ,
diurnal pH-carbon dioxide curves and oxygen curves, may well be the
best methods for measuring productivity in shallow or flowing systems,
especially when modern instruments are considered (Beyers, _e_t all. ,

1959).
Artificial Substrates and Pigments

Artificial substrates were first used mostly to collect periphyton
or "aufwuchs" for qualitative purposes. Hentschel (1916) is usually
credited as the first to employ artificial substrates in aquatic studies
and during the 10 to 20 years that followed, most use of artificial sub-

strates was carried out by EurOpean biologists.

Much of the work in the United States has been concerned with the
adequacy of samples obtained by artificial substrates. Young (1945)
claimed that the periphyton composition was governed in part by the
type of substrate. Newcombe was one of the first to measure pro-
ductivity with glass slides and in 1949 and 1950 he reported results
claiming that representative groups of periphyton did attach to glass
slides and that horizontally placed slides were probably better than
those placed vertically. -Newcombe ($1. cit.) decided the best criteria
for exposure time was the time necessary to produce an amount of algae
adequate for laboratory analyses. Castenholz (1960) also found glass to
be non-selective regarding algal colonization and used a two to four
week exposure period for productivity measurements.

The few references cited here are by no means an indication of
the amount of work that has been done concerning artificial substrates.
Much of this work has little or no bearing on productivity measurements
and has not been included here, but may be found in a comprehensive
review by Cooke (1956).

The dependence of the photosynthetic process upon chlorophyll
led to the use of the optical density or weight of pigment extracts as a
measure of production. The early use of pigment extracts was mostly
by workers in marine areas. Kreps and Verjbinskaya (1930) were among
the first to use this technique. Harvey (1934) contributed considerable
information about the use of pigment extracts and for many years the
pigment unit developed by him was used. . This pigment unit was called
the Harvey Plant Pigment Unit (HPPU) and, as expressed by Harvey,
was based on acetone extracts of plant pigment per cubic meter of water.
Manning and Juday (1941) also gave detailed procedures for using chloro-
phyll measurements to estimate primary production. Gardiner in 1943
used acetone extracts and at that time pointed out the need for more

research into the accuracy and limitations of the pigment method.

10

Some researchers have tried to correlate pigment extracts with
other parameters to test the validity of the pigment method. Juday,
Blair, and Wilda (1943) compared chlorophyll extracts with oxygen
measurements and with the dry weight of plankton and reported that
chlorophyll varied from . 39 to 1. 06 percent of the dry weight of plankton.
Tucker-(1949) compared pigment extracts with cell counts and calculated
correlation coefficients of . 78 to . 97 for the pigment and cell count
regressions. Grzenda andBrehmer (1960) credited work by Hooper,
Ball, and Hayne (ms) as the first to combine artificial substrates and
pigment extracts as a method to study productivity. Grzenda and
Brehmer (_o_p. git.) correlated theroptical density of phytopigments,
extracted from periphyton collected on plexiglass shingles, with the ash-
free dry weight of the periphyton. Peters (1959), using the same tech-
nique, found that the same regression relationship for phytopigment to
organic weight was valid-for a number of diatom communities and also
stated the possibility of the same relationship being valid for most of
the seasons with the exception of the low productivity of winter.

There have been many criticisms of the pigment extract method.
Most of the criticisms are concerned with the fact that the relationship
of chlorophyll content with organic weight is not consistent, but is in-
fluenced by a number of factors such as nutrition, light intensity,
species, and age of the algae. Myers and Klratz (1955), studying blue-
green algae, reported that there was no relationship between photosyn-
thetic rates and pigment content. Other controversies have been con-
cerned with the proper solvent to use for pigment extraction since
the absorbancy spectrum varies with the type of solvent. Until recently
the role, in photosynthesis, of pigments other than chlorophyll a has
been unknown and many discussions have been concerned over whether

or not only chlorophyll a should be used in the pigment method.

11

Despite the many controversies over the use of the pigment method,
it still remains a rapid and attractive method. (As Odum (1959) points
out, the chlorophyll content of communities appears to be much-more
consistent than that (if individual species and may be an example of

"c ommunity homeostasis . "

c” and Other Methods

The following methods were not employed in this study, but are
briefly discussed because of their importance in production studies in
general.

‘Probably the oldest method of measuring production or more
likely, standing crop, is that of enumeration and the measuring of
volumes of plankton. -Enumeration is possible for those algal forms
occurring as single cells, thus including most planktonic species and
most of the attached diatom flora. Counts are made in Sedgwick-Rafter
cells or on membrane filters and reported as number per volume of
water. . Enumeration fails to give any idea of biomass. The volume of
plankton per given volume of water has been used considerably and
is measured by concentrating the planktonic forms by centrifugation
or by filtration. The accuracy of this method for measuring primary
production is lowered by the difficulty of separating zooplankton,
detritus, and inorganic particles from the phytoplankton. Studies
typifying the early use of enumeration and volumes as methods are
those of Kofoid (1903, 1908), Birge and Juday (1914), Weibe (1930), and
Ruttner (1930).

One of the most recently developed methods to measure primary
productivity is that employing the radioisotope C14. Steeman-Nielsen,
in 1952, first described the use of C14 in combination with the L-D bottle

method as a means of measuring the amount of carbon fixed during

12

photosynthesis. Since then the C14 method has received much attention
andcritical evaluation. One of the major points has been whether the
C14 method measures gross or net production or possibly some inter-
mediate value. Doty and Oguri (1959) have made extensive studies of
the C14 method and probably give the most recently established

procedures.

Stream Studies

A recent, extensive review of the ecology of river algae by Blum
(1956) makes one point readily apparent, that is, in general river studies
have been mostly on plankton and mostly qualitative with only a few
quantitative benthic studies. The review presented here has been
selected to cover the earlier work and those studies dealing with either
production or benthic algae or both.

-Kofoid's studies (1903, 1908) of the plankton of the Illinois River
are some of the earliest and most noteworthy stream investigations.
~Kofoid's studies (_c_>_p_. c_i_t.) were very detailed and included the effects of
various factors on plankton, measures of the production of plankton in
cubic centimeters, and the importance of plankton to fish production.
Another quantitative study of river plankton was undertaken on the
San Joaquin River in California by Allen (1920). One of the first studies
to deal with periphyton rather than plankton was a taxonomic investi—
gation of the "blanket algae” of freshwater pools by Platt in 1916.

A study by Eddy (1925) dealt with the description and succession of algal
cover on a stream bottom.

Observations of the diurnal gas variations in rivers were made
as early as 1928 in England. Oxygen and pH measurements were made
continuously over 24 hour periods revealing an oxygen maximum shortly

after mid-day and highest seasonal values in the spring along with heavy

13

diatom growth (Butcher, (it a_._l. , 1928). Observations of diurnal gas
variations such as these probably played a part in the development of
diurnal gas curves for the measurement of productivity. The work of
R. W. Butcher (1932, 1946), although not primarily concerned with
productivity, contributed significantly to the knowledge of periphyton
ecology and the use of artificial substrates in streams. ‘Kann (1933)
also studied the ecology of periphyton, but in the littoral zone of lakes,
and reported the effects of wave action and temperature on algal types.

- Whitney (1942) observed the diurnal fluctuation of pH and oxygen
in a stream and noted that the peaks of the two occurred together, but
he made no use of the data for production estimates. 1 Some recent
stream studies have continued to be primarily concerned with taxonomy,
distribution, and the general ecology of periphyton (Blum, 1954, 1957,
Gumtow, 1955, and-Douglas, 1958). But, many of the recent works
have dealt with primary productivity. Abdin (1949) measured the
number of diatoms per square centimeter that attached to glass slides
and Gumtow (1955) measured standing crop of periphyton by number
and by volume. The detailed investigations of Odum (1957a, b) initiated
the use of diurnal oxygen curves to measure primary productivity in
flowing waters. Hoskin (1959) also used diurnal oxygen measurements
to estimate the productivity of streams in North Carolina. .In a study
of a mountain stream, McConnell and Sigler'(l959) used relative
chlorophyll concentrations and L—D bottle methods to measure the algal
productivity. Grzenda (1960) combined diurnal oxygen measurements,
periphyton collections on artificial substrates, and chlorophyll extractions
to estimate the primary productivity of a warm-water stream in Michigan.

The increase of research on stream productivity indicates a
trend which will help to fill an existing gap in our knowledge of stream

ecology.

14

Related Topics and Reviews

There are a number of physical and chemical factors influencing
the physiology of aquatic flora and thus affecting photosynthesis and
productivity. An immense number of studies have dealt with these
factors, both in nature and in cultures. The use of cultures dates
back at least to the work of Allen and Nelson in 1910 and the use of algal
cultures by plant physiologists and plant biochemists has been very
extensive since that time.

Solar radiation, both in quantity and quality, was one of the factors
most thoroughly investigated by researchers. in the early 1900's. The
first studies were concerned with light penetration into water (Pietenpol,
1918, Atkins, 1926a, and Klugh, 1927). Birge and Juday (1929, 1930,
1931, 1932) published a series of reports on the transmission of solar
radiation by lake water. Klugh (1930) studied and reviewed the effects
of light quality on photosynthesis. Solar energy was studied by Schomer
and‘Juday (1935) regarding production efficiencies at different depths
and by Jenken (1937) regarding energy values by spectral quality.

More recent work on light intensity has been undertaken by Dvihally
(1960), . Kratz and Meyer (1955), Myers (1946), (Saito (1958), and Warburg,
SchrESder, and Gattung (1956). rRecent work on light quality has been
done by McLeod (1958, 1961), and Warburg and Krippahl (1960) among
others.

Temperature effects have usually been studied in cultures and in
terms of a 010 and have been reported by many authors including Saito
(1958), Talling (1955), Osterhout and Haas (1918), and Van der Paauw
(1934).

The biochemical composition of algae has been reported by a
number of workers, notably Birge and Juday (1922), Juday (1940),
Ketchum and» Redfield (1949), .Krogh, -Lange, and Smith (1930), Schuette
(1918), and Spoehr and Milner (1949).

15

Photosynthesis and nutrient requirements have received so much
attention that no attempt has been made here to review these two sub-
jects. Rather, a number of reviews and comprehensive publications
are cited here. The subject of algal nutrition is well covered by
Barnes (1957),. Burlew (1953), .Fogg (1953), and Rodhe (1948).
.Photosynthesis has been reviewed and discussed in detail by such authors
as Arnoff (1957), Franck and Loomis (1949), Hill and Whittingham (1955),
Rabinowitch (1945, 1951, 1956), and Whittingham(l955).

Other reviews are given by Prescott (1956) on algal ecology, and
Saunders (1957) on growth factors of algae. A review by Lund and
Talling (1957) on algae and limnological methods is especially compre-
hensive, as evidenced by 777 references, and Strickland (1960) gives a
good account of primary production measurements of marine phyto-

plankton.

METHODS AND EQUIPMENT

Artificial Streams

A matched pair of artificial, recirculating streams were used
for this study with one of the streams being built to conform to the
first, existing streamdesigned and used by Stokes (1960). The streams
were 24 feet long, 14 inches wide, and 10 inches deep and were con-
structed of six sections of aluminum trough each four feet long
(Figure 1). The troughs were lined with clear polyethylene sheeting.
The return flow passed from the lower end of the streams, through
black polyethylene filter boxes, and by black polyethylene tubing, . 1. 75
inches in diameter, to the reservoirs located below the troughs. The
reservoirs, each with a 300 liter capacity, were also lined with poly-
ethylene sheeting. Identical Homart sump pumps, . Model 259.481, were
used to pump the water from the reservoirs through polyethylene tubing
to the upstream end of the troughs. Plexiglass baffle plates reduced
theturbulence of the inflowing water.

The troughs were supported from below, at the union of each
section, by threaded bolts inserted in heavy metal cross pieces. The
support bolts, with two inch plates welded to the heads, and the metal
cross pieces were both movable vertically. Thus the ends of each four
foot section could be raised or lowered to create pools or to give the
streams the desired gradient. The streams were separate except for
valved tubing connections between the return tubes to the reservoirs
and between the delivery tubes to the upstream ends. The water of the
streams could be intermixed or maintained separately as desired.
Valves were also located on the the return tubes and on the delivery tubes

making it possible to control the discharge of the streams.

16

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19

The Opaque filter boxes, each witha graded series of aluminum
screens, and the reservoirs provided sufficient area for decomposition
of organic (matter. The lining, filter boxes, and tubing, all of poly-
ethylene, provided chemically inert channels for the water. The few
metal exposures, that is,the valves, pump base, and filter screens,
were sprayed with clear Krylon plastic paint.

. The two streams were covered with clear polyethylene sheeting
and the filter boxes and reservoirs were provided with opaque coverings.
The loss of water by evaporation and contamination by dust were thus

reduced to a minimum.

-Nutrient Medium

The streams were each established with 246 liters of distilled
water in July, 1959. An inorganic nutrient medium was selected to supply
the elements necessary for algal growth. The medium selected was
modified from media given by Chu (1942) and by Kratz and Meyer (1955).
The composition and concentrations as first added appear in‘Table 1.
The streams were allowed to Operate on this medium until May, 1960
when additional nutrients were added (Table 2). As shown in Table 2,
other nutrients were also added in‘July and October of 1960. ~A nutrient
stock solution was used to replace nutrients lost by removal of water
samples and algalwsamples. The stock solution for nutrient. replace-
ment contained elements in the following concentrations (milligrams per
milliliter): Ca -- 1.02, Mg -- 0.18, Na -- 0.59, N -- 0.93,»P -- 0.13,
and Si -- O. 25. All nutrients were dissolved in distilled water before
being added to the streams.

Within a few days after a nutrient addition the streams reached a
steady nutrient state with the nutrient supply recycling by decomposition

of algae in the filters and reservoirs. This situation was assumed to

20

Table 1. The composition of initial nutrient medium in milligrams per
liter added to each stream in July, 1959.

 

 

Salt Concentration Element . Concentration

KNO3 114 K 47 . 6

‘KZHPO4 8 N 15. 7
MgSO4' 7HZO 40 Mg 4 . O

'CaCO3 40 Ca 16 . 1

\FeC13 4 Fe 1. 8
NazSiO3- 9HZO 19 Si 1. 8

' EDTA 41 P 1 . 4
Microelements):< 1 m1 liter”1 Cl 2. 2

Na 3 . 0

C 4. 8

S 5 . 2

 

 

'Stock solution of micronutrients (grams per liter):

H3BO3 "" 2.86 (NH4)6MO7OZ4'4H20 -- 0.18
MnClZo4HzO -— 1.81 cuso4 -— 0.05
ZnSO4-7HZO —- 0.22 Co(NO3)2°6HzO —- 0.49

be comparable to the boil of a spring continuously supplying nutrients.
The concentration of nitrate and phosphate, determined by water
analyses, was similar to the values reported by Odum (1957b) for some
Florida springs.

-Ethy1ene diamine tetra-acetic acid (EDTA) was only used with
the first nutrient additions since certain following studies were concerned

with effects of chelates.

21

Table 2. The concentration of elements in milligrams per liter added
to each stream on May 24,, July 21, and October 7, 1960.

 

 

 

Concentration
Element May 24 July 21 and October 7
Ca 8. 0 0. 41
Mg 1. 8 0. 73
Na 4 8 O. 24
N 8. 1 0. 38
P 1. 0 0. 05
Si 2. 0 0. 10
Microelements* - 0. 5 ml liter“l

 

>l

"Micronutrient stock solution as given in Table 1.

Light

Radiant energy was supplied to each stream by a row of 12
incandescent bulbs suspended approximately an equal distance above
the stream bottom. Each bulb was equipped with a 14 inch shade re-
flector. The bulb size and the height of suspension depended upon
the particular study. Incandescent bulbs were used because of the
predominance of the longer (red) wavelengths over those of fluorescent
bulbs having a predominance of the shorter (blue) wavelengths.
Although chlorophyll extracts show a higher absorbancy peak in the
blue range, the action spectrum of the living cells is greatest in the
red range, especially in blue-green algae where phycocyanin absorbs
at about 625 mu (McLeod, 1958,. Rabinowitch, 1951). Also, Meier
(1932) reported lethal effects of ultra-violet light on a green alga

and the use of incandescent bulbs avoids any adverse effects of UV light

22

more so than would most fluorescent bulbs. The heat from the incan-
descent bulbs was dissipated before it passed through the polyethylene
cover of the streams.

The photoperiod for each stream was controlled automatically by
a-Paragon Electric Company timer, Model 7008-0 which turned the
lights on and off at pre-set times depending upon the particular study.

The amount of light delivered to the streams was determined by
two methods. Illumination was measured with a Norwood Super Director
exposure meter set for incident readings. .The exposure meter was
calibrated directly with an Eppley pyrheliometer and a graph was drawn
to convert illumination readings to energy units (Figure 2). The linear
relationship in Figure 2 is possible for only a small segment of the
calibration as the overall relation is curvilinear. Measurements were
also made with a Weston Foot Candle Meter, Model 614. Values read
in foot candles were converted to energy units using the conversion
factor of 1 ft-c = 6.58 x 10'5 g cal cm"2 min '1 given by Strickland (1958)
for the photosynthetic range of wavelengths.

, Energy values underwater, at the surface of the algae, were
determined directly by the exposure meter wrapped in Dow Saran Wrap
and by calculation. Calculations of underwater values were based on
surface measurements with the foot candle meter and absorptionco—
efficients (_k)‘ determined from exposure meter readings and from values
in the literature for the major wavelengths of incandescent light and dis-
tilled water.

1 Absorption coefficients were calculated for three depths using
Lambert's Law, I = Ioe‘kx. The values for 15 decreased with increasing
depthland probably correspond to those wavelengths that were pre-
dominant at that depth (Table 3). The calculated 5 values range from
. 257 to .0631 at 1. 27 cm to 6. 35 cm of water depth respectively,

corresponding to wavelengths of about 650 mp (red) to 580 mp. (yellow).

23

Figure 2. Conversion of exposure meter readings to
energy units.

.Energy units (g cal cm'?‘ min'l)

 

24

 

 

 

(foot-candles)

Exposure Meter Readings

Figure 2

. 05 -

Small segment used in study.

Actual line from measurements at
. 04 - higher light intensities showing /

curvilinear relation.
. 03 _
. 02 _
. 01 1
' 00 J'W/‘T' 7 n r

3 4 5
(f-stops)
1 r T
200 300 400

25

This range of wavelengths is in agreement with the spectrum of incan-

descent bulbs .

Table 3. Absorption of light in artificial streams.

 

Absorbancy by

 

 

 

 

‘-Percentage Absorption coefficient (3)
Artificial ‘ Sea )2 Artificial Wavelengths (mg) for
Depth streams -Water streams corresponding 15
I p 3:"? >:<>:<>:<

0.5 cm - 21 .257 610 710

1. 27 cm 28 - . 0934 590 620

6.35 cm 33 - .0631 570 590
100. 0 cm — 50

 

>i<
Richardson, 1933 .

>:<>:<
James and Birge, 1938, measurements of monochromatic light in

pure water .
a}: ,:.

‘ PStrickland, 1958, measurements of monochromatic light in pure
water.

The conversion of underwater illumination measurements to energy
values is based on a report by Dvihally (1960) claiming that, at depths,
illumination units and energy units are more proportional for the long

wavelengths than for the short wavelengths.

Water T empe rature

The water temperature of each stream was regulated by a thermo-
statically controlled refrigeration unit with the cooling unit located in
the reservoir. Temperature was regulated within a range of :1: 1.0 C

and was recorded by a Taylor thermograph for weekly periods alternately

26

in the two streams. Water temperatures were also checked periodically
with a hand thermometer. The water temperature was measured each

time a water sample was taken for oxygen analysis.

Water Velocity and Discharge

The velocity of flow and discharge were controlled by adjusting the
inlet valves and the gradient of the streams.

The best estimate of flow velocity was calculated from discharge
measurements and the stream dimensions. The actual discharge was
measured with a volumetric container and a stop watch at the reservoir
outfall. The product of stream width and depth divided into the dis-
charge gave the average velocity at the point where the dimensions were

measured.

Specific Conductivity and Total Solids

The amount of dissolved materials in the streams was primarily
a result of the salts added as nutrients and the recycling of elements
from the decomposition of algae.

Electrical resistance was measured with a Model RC-7 conductivity
meter manufactured by the Industrial Instruments Company. Readings
were corrected to 18 C and expressed as the reciprocal of resistance,

1. e. , micromohs per centimeter.
Total solids were measured gravimetrically as described for total

residue in "Standard Methods for the Examination of Water, Sewage and

 

Industrial Wastes" (APHA, AWWA, FSIWA, 1955).

 

27

Alkalinity, pH, and Carbon Dioxide

Alkalinity, pH, and carbon dioxide are interrelated and, in the
artificial streams, were primarily a function of the calcium and
magnesium that were added as nutrients and of the buffer system.

The addition of calcium and magnesium combined with atmospheric
carbon dioxide diffusing into the water forms the carbonate-bicarbonate
system as follows:
coz -+ H20 4—; H_,_co3 4.,— H+ + Hco3'
Ca(HCO3)2 #Ca++ + 2HCO3”
HCO3" "=5 CO3: + H+
co; + H,O’=-;Hco,‘ + OH'

It can be seen from the formulas that as carbon dioxide enters the
system more hydrogen, bicarbonate, and carbonate ions are formed.
- When calcium and magnesium ions are present they combine with the
bicarbonate and carbonate ions until an equilibrium is established.
The alkalinity and pH thus depend largely upon the carbon dioxide tension
and the availability of combinable cations.

Alkalinity was determined by the method described by Welch (1948).
The pH was measured with a Beckrnan Model H-2 pH meter. The concen-
tration of free carbon dioxide was determined by nomograph making use

of measurements of pH, alkalinity, total solids, and temperature

(APHA, AWWA, FSIWA, 1955).

Pho spho ru 3

Phosphorus was added equally to both streams as one of the
nutrient elements. Phosphorus concentrations in the streams were
monitored for two reasons: 1) the role of phosphorus as a nutrient is

important, and 2) the concentration of phosphorus was probably as low

28

as any of the major elements in the streams, as is often the case in
nature.

. Concentrations of total and dissolved phosphorus in water samples
were determined by the ammonium molybdate-w-‘stannous chloride method
given by Ellis, Westfall, and Ellis (1948). Samples for total phosphorus
were digested while those for dissolved phosphorus were treated
directly with the color-producing reagents before being read in a Klett-
Summerson colorimeter using a red filter.

The concentration of cellular phosphorus in algal samples was
determined to provide a measure of the phosphorus metabolism of the
algae. -Organic phosphorus of prepared algal samples was determined
using the same procedures as for total phosphorus. The samples of
algae were ashed in a muffle furnace and weighed prior to the phosphorus

analysis .

Nitrogen

Nitrogen was also added equally to both streams as one of the
nutrient elements. Nitrogen was determined in water samples and algal
samples for the same reasons as was phosphorus.

The concentration of available nitrogen-(NH:- +< NO; + N03) in
water samples was measured by the reduction method while the organic
nitrogen of algal samples was determined by the micro-’Kjeldahl pro-

cedure; both methods being described in "Standard Methods for the

 

Examination of Water, Sewage, and Industrial Wastes" (APHA, AWWA,

 

FSIWA, 1955). Color was produced by nesslerization in the reduction
method and readings were made with a Klett-Summerson colorimeter
using a green filter. Boric acid and titration with O. 02 N H3804 were
used for the organic nitrogen. Algal samples were oven dried at 55 C

and weighed prior to organic nitrogen analysis.

29

Calorimetry

It was necessary to know the caloric value of algal samples to
calculate energy efficiencies, to compare the energy content of algae
grown in different areas and under different conditions, and to gain
some insight into the composition of the algae.

Duplicate samples of algae were analyzed for each caloric
determination. The measurements were made with a‘Parr Oxygen Bomb
Calorimeter, plain type, series 1300, using the method described in

"Ox en Bomb Calorimetr andCombustion Methods" (Parr Instrument
1L Y

 

Company, 1960). All algal samples were oven dried at 55 C, powdered,

pelleted, and weighed in preparation for the analysis.

Weights

All gravimetric measurements were made on an analytical balance
and were recorded when two successive readings of i 0. 5 mg were made.
Dry weight was determined after drying in an oven at 55 C. Ash-free
dry weight, assumed to be organic weight, was measured after ignition
of the sample at 550 C in a muffle furnace. All weighings were made

after the samples had cooled to room temperature in a dessicator.

Primary Productivity

The rate of energy transformation from light energy into organic
matter was measured by three methods which are discussed in the
following paragraphs. Three methods were used as a comparative study
in an effort to determine the most satisfactory method for use in flowing

waters. In the final comparisons, all values were converted to calories.

30

Diurnal Oxygen Curve 5

 

The amount of oxygen evolved by the algae during photosynthesis
was estimated using the upstream-downstream method given by Odum
(1956). The upstream station was located just before the first incan-
descent bulb and the downstream station was located under the last
bulb. The difference between the oxygen concentrations of the upstream
and the downstream stations was a measure of net production for the
stretch of water under the lights. Respiration was automatically sub-
tracted. Since there were no springs or seepage, no oxygen could be
added by drainage accrual. It was necessary to correct for diffusion

using the formula given by Odum (pp. _c_1:t.).

D:KS

where D = the diffusion rate per area (g 02 m"-2 hr'l),

K = the gas transfer coefficient at 0% saturation
(g 02 III-2 hr'l),
and S = the saturation deficit between water and air.

- Efforts to calculate the gas transfer coefficient, K, produced incon—
sistent results, so values for K were estimated from tables given by
Odum (pp. c_i_t.) for comparable water conditions.

The estimation of gross productivity requires the measurement of
respiration. Respiration was estimated from oxygen concentrations
measured after the lights were turned off using the corresponding
diffusion corrections.

All estimations of production and respiration were calculated in

volume dimensions, g 02 m--3 hr ‘1, and were converted to area

'1, by dividing by the mean water depth between

dimensions, g Oz rn'-‘2 hr
the stations. The conversion to area measurements was done to facilitate
comparison with data from artificial substrates already on an area

basis.

31

Three estimates of productivity, in g 02 m'2 day‘l, were made
from the oxygen data. These were gross productivity for the area
under-the lights, net productivity for the same area, and net productivity
for the entire stream including the filter and reservoir. -Net productivity
for the entire system required the estimation of respiration and'B. O. D.
inthose stream areas in darkness. -Respiration and B.VO.AD. were
determined by reversing the oxygen calculations of the upstream-down-
stream method and correcting for diffusion. It was thusassumed that
the difference in oxygen concentration between the downstreamstation
and the upstream station was due to respiration and B. O. D. when the
water passed through the filter and reservoir.

1A typical oxygen curve is given in Figure 3 and a sample calcu-
lation of productivity is given in Table 4. It was found, as expected,
that the area under the curve agreed with calculated estimates.

All oxygen concentrations were determined by the Alsterberg

(azide) modification of the Winkler method as given in ”Standard Methods

 

for the Examination of Water, Sewane, and Industrial Wastes" (APHA,

 

AWWA,-FSIWA, 1955). Oxygen saturation values for use in diffusion
corrections were corrected for temperature, atmospheric pressure,
and vapor pressure. Water samples for oxygen determinations were
taken from the same water mass as it passed from the upstream to the

downstream stations.

Diurnal pH-Ca‘rrlbon dioxide Curves

 

The uptake of carbon dioxide by algae during photosynthesis was
measured as an estimate of productivity. Measurements were made
indirectly by recording pH changes and converting these changes into
carbon dioxide concentrations using the method described by Verduin
(1951, 1956). Conversion graphs (Figure 4) were made stepwise, by
bubbling respired air through water samples and back-titrating with

0.02 N NaOH (Verduin, 1960).

32

Figure 3. Rate of oxygen production in stream 1No. 2 during
the temperature study, on June 28, 1960, . as
estimated by the area under the curve method.

33

 

 

 

 

 

 

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Area under curve

 

 

 

 

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Time (hrs)

Figure 3

34

 

 

 

Table 4. Production rate of oxygen in stream‘No. 2 as calculated from
measurements taken on June 28, 1960 during the temperature
study.

>:< >’ >:<
(A) (B) (c = A+B) (D = C+R) "
Oxygen Oxygen Oxygen Gross

Time change Diffusion corrected corrected production
(g m‘3hr‘l) (g m'3hr'1) for for (g m'3day'1

diffusion respiration
(g m-3hr'l) (g m’3hr'1)

7AM -0.08 -0.21 -0.29 0.14

9 0.60 —0.15 0.45 0.88

11 0.80 —0.13 0.67 1.10 '15: 1.081,

1 PM 0.96 -0.13 0.83 1.26 1.081x12 hrs.

3 0.92 —0.13 0.79 1.22 = 12.98

5 0.76 -0.13 0.63 1.06

7 0.72 -0.18 0.54 0.97

9 -0.08 -0.20 -0.28 0.15

 

>fiDiffusion is based on a gas transfer coefficient, 1K, of 1. 75 g In"3 hr'1 at
0% saturation, e. g. , the saturation deficit at 7 AM = 12% and (B) =
1.75 x12 = -0.21.

>:< >:<

R is respiration and is based on measurements taken at night and cor-
rected for diffusion. R for this estimate equals 0.43 g In-3 hr’l.

Net production ‘ Gross production - R = 12. 98 - (0.43 x 12 hrs.)

7.84 g m-3 day'l.

35

Figure 4. Titration curves of stream water for conversion
of change in pH units to pmoles of carbon dioxide.

0.02 N NaOH (ml)

0.02 N NaOH (ml)

2.

l.

O.

2.

0.

36

 

 

 

 

 

 

 

 

pH
Figure 4

' Stream 2
0—0 June 28, 1960 A
O _. II/ '400
U-—-—0 January 22, 1961 )(g/
A ----- A March 3, 1961
-300
0 — ~200
~100
r f I T T O
7.8 8.0 8 2 8.4 8.6 8.8 9.0
Stream 1
0—0 June 28, 1960 f
0 - / "400
D— --0 January 22, 1961 n/
./
/
A-mA March 3, 1961 ,/
'300
"200
*100
0 r r m r r 0
7.8 8.0 8 2 8.4 8.6 8.8 9.0

pmoles COZ

umoles COZ

37

A number of criticisms have been made. about the methods. used to
construct the pH-carbon dioxide conversion graphs. -An attempt was
made to interpret and avoid these criticisms as‘much as possible.

It has been pointed out that curves made by titrating with different
solutions, i. e. , acids, bases, and CO; water, diverge from each other
except in the range above pH 7. 8 where the agreement is good (Beyers
and Odum, 1960, Verduin, 1960). The range of pH change in'the
artificial streams was primarily from pH 7.9 to 9.0. -Lyman (1961)
pointed out that titrations with solutions altered the alkalinity of the
sample and thus produced an error. If the titration is done stepwise
using several samples, each one for a small range of the titration
curve, then the amount of titrant used for any one sample is slight and
the titrant does not accumulate enough to cause an appreciable error
(Verduin, 1961). In the single step titration the titrant accumulates

enough to change the alkalinity during the latter part of the titration.

Figure 4 shows the conversion curves for different dates to
deviate slightly and demonstrates the value of preparing a curve for
each productivity estimate. Only three curves for each stream were
used in this study with the curve of the closest date and water conditions
being used for the particular productivity estimate.

. Diffusion of carbon dioxide into or out of the water was considered
to be negligible. Beyers and Odum (1959) state that no diffusion cor-
rection is ordinarily needed with the pH-carbon dioxide method.

Verduin (1956) states that even at maximuminvasion rates, the air-
water phase boundary is an effective barrier to carbon dioxide. The
conditions of pH, alkalinity, temperature, and total solids in the artificial
streams were such that the range of free carbon dioxide in the water was
from 0. lto 1. 5 mg liter-1. At the lowest pH (7.8) a small amount of
carbon dioxide may have left the system, while at the highest pH (9. 0)

a small amount may have entered the water.

38

The pH was found to increase throughout the day and to decrease
throughout the night, thus the maximum change could be recorded by
measurements made at the beginning and end of the daily photoperiod.
The maximum pH change was converted by graph to micromoles of
carbon dioxide.

The measurement of carbon dioxide uptake is an estimation of
net productivity. Gross productivity is calculated by adding respiration
to the net productivity. The diurnal carbon dioxide curves revealed
respiration at night to be equal to net productivity during the day
(Figure 5). Thus gross productivity was twice net productivity.

. Carbon dioxide estimates were made on the same days as the
oxygen measurements. Samples for pH were taken at the lower end of

each stream.

Periphyton Gr owth . and Pigment Extraction

 

The third method used to measure net productivity was the gravi-
metric analysis of periphyton collected on artificial substrates. ~ A fourth
method, phytopigment analysis, was also tested, but it gives the same
values as the periphyton growth upon which it is based. The phyto-
pigment method is therefore an alternate method to be used after corre-
lations between periphyton weight and phytopigment concentration have
been established.

Plexiglass shingles, with an exposed area of 1. 5 square decimeters,
were placed on the stream bottoms at five designated stations.

Periphyton colonized the shingles and was allowed to grow On these
substrates for a period ranging from 12 to 28 days. The substrates
remained in the streams for the longer periods when the periphyton

growth was slowest. A pair of substrates from each station gave a total

of 10 used for each estimate of productivity for each stream. The accumu-

lated growth from the paired substrates was combined to produce a more

39

Figure 5. Diurnal carbon dioxide curve prepared from pH
measurements in stream No. 2 during the
temperature study on July 5, 1960.

CO; Changes (mmoles m‘3)

40

    
 

 

 

OI
.CO; evolution
100 1
CO;
\\
2004 \ \
\
\ \
\
\

Theoretical line H \

extended to estimate ‘ \

gross productivity}< \ \
300~ \\

\
\
\\
I I l ’ l I I
8 AM 12 4PM )l‘ 8PM 12 4AM
dark

light
Time (hrs)

Figure 5

>'cNet productivity 2 175 -mmoles CO; m-3 day"1 or 7. 7 g CO; rn"3
day'l. Assuming day respiration equals night respiration, then
extended line (dashes) is gross productivity (350 mmoles CO;

In"3 day'l).

41

representative sample for eachmeasurement. .Calculations based on
data collected by Stokes (1960) revealed growth from 63 paired sub—
strates to have a mean coefficient of variation of 16. 3% with a range
from o to 140%.

8A procedure was used allowing measurement of both total weight
and phytopigment concentration from the same sample. The periphyton
was scraped and rinsed from the substrates into 95% ethanol and allowed
to stand in darkness for at least 48 hours. Filtration through a mem-
brane filter (pore size = 0.45 mu) separated the periphyton from the
ethanol-soluble phytopigments. The phytopigment extract was adjusted
to 50 ml and the concentration measured with a Klett-Summer son
colorimeter using a red filter (640 - 700 mu). After the phytopigment
reading, the extract was recombined with the periphyton in an evaporat-
ing dish, dried at 55 C, and the constant weight determined on an
analytical balance. Ash—free dry weight, assumed to be organic weight,
was then determined after ignition of the sample at 550 C.

The periphyton weight in grams was divided by the number of
days that the substrates remained in the streams, less a six day coloni-
zation period, to give net productivity in g m‘z‘ day’l. The amount of
algae that grew on the substrates during the colonization period was too
small to be measurable. (Phytopigment concentrations were corrected
for a deviation from the Lambert-Beer Law and reported as phytopig-
ment units as described by Grzenda and Brehmer (1960). Calculated
regressions allowed conversion of phytopigment units to organic weight
of periphyton.

The conventional use of a wavelength of 660 mg or a light passing
through a red filter to measure the absorbancy of phytopigment extracts
is based on the absorbancy peak of chlorophyll _a_. Chlorophyll _a_ is
believed to be the main pigment involved in the transfer of light energy

and is a major pigment in all of the algal groups thus providing the basis

42

for its use as a standard. The absorbancy peak at 660 mu is fairly
well isolated from peaks of other pigments except forrchlorophyll _b_

in which the absorbancy peak is about 645 mu (Strickland, 1960). The
influence of phycocyanin, with a peak at 615 mu, may have a slight
effect on the absorbancy reading especially if a wide wave band is used.
It is assumed here that the influence of phycocyanin in the pigment
investigations will have little or no bearing on comparisons made with
other pigment studies other than to compensate for chlorophyll 2,
present in the Chlorophyceae, and chlorophyll E in diatoms (peak at
630 mu), both of which are reported to be lacking in the blue-green

algae (Strickland, c_>_p_. c_i£.).

STANDARD CONDITIONS AND STUDY PROCEDURES

Manyof the physical characteristics of the artificial streams were
controlled and altered for the various studies that were undertaken.
-A description of these characteristics in the standard and study conditions
is a necessary prelude to the presentation of results.

The standard conditions of a characteristic were in effect in both
streams except when that characteristic was being studied (Table 5).
The characteristics studied were temperature, photoperiod, light in-
tensity, current velocity, and chelates. {Other relevant characteristics,
not specifically studied, are shown in'Figures 6 and 7. The characteristic
altered for study was 'maintained in most cases for at least one month.
Diurnal oxygen and pH measurements were usually made for each stream
at the end of the second and fourth weeks. Substrates were removed at
the same two week intervals, except during the current velocity study.
The growth pattern of the algae was also studied during the current
velocity study. For the growth pattern the substrates were removed
from the streams in such a manner that growth measurements were made
by two or three day increments from 3 to 34 days. After each study period
the streams were maintained under standard conditions for at least two
weeks to return the two streams to an equal productivity level.

The velocity of flow as given in Table 5 appears to be very slow
when compared to natural streams. The highest velocity recorded was
4.2 cm sec-1 in the riffle area of stream 1. Odum and Hoskin (1957),

in a study of a laboratory stream microcosm, referred to velocities of

1 1

8 to 20 cm seC' as high and those of 2 cm sec" as low velocities and
explained that these were the velocities occurring very near (2. 5 mm)
the algae and thus correspond to much higher velocities in a natural

system.
43

44

Table 5. Standard and study conditions in the artificial streams.

 

 

 

Study Condition Standard Condition?"
Characteristic Stream .1 (Stream 2
Temperature 20.0 25.6 23. 9
(degree C)
Stream Velocity
(cm sec-1)
pool 0. 6 0. l 0. 5
Riffle 4.2 0.6 2.5
Radiant Energy
(g cal m-Z day--1
at water surface 63, 000 136, 800 68, 200
at algae surface 44, 200 95, 000 48, 240
Photoperiod
(hours) 4 on - 12 on - 12 on-
4 Off 12 Off 12 off
Chelate
(mg liter-1) 30 10 trace

 

’PThestandard condition of a characteristic was in effect at all times
except when that characteristic was being studied, e. g. , the streams
were always at 23. 9 C except during the temperature investigation when
thestudy temperatures were in effect. Standard conditions were the
same for both streams.

45

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47

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48

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49

Theartificial streams were established in the summer of 1959 and
used for pilot studies until the first study was initiated in the summer
of 1960. This time also served as a period for colonization, (algal
succession, and equalization of the two streams at a steady state. The
streams were seeded by introducing a few periphyton-covered stones
taken from a local warm-water stream, the Red Cedar River.
Colonization required only a few weeks and the first periphyton was a
mixture of green and blue-green algae, and diatoms. Succession moved
toward a climax species and a steady nutrient state. The first alga to

become dominant was Palmellococcus s2. Chodat, an ellipsoidal, green

 

alga, which after a few months gave way to a blue-green alga, - Plectonema

 

Boryanum Gomont, identified by Dr. G. W. Prescott. This small,
filamentous alga represented the climax species and was dominant through-
out the remainder of the study. Odum (1957a) states where environments
become extreme for any reason the number of species decreases. The
artificial streams, like Silver Springs studied by Odum (pp.~c_it.), were
extreme in being stable and this accounts for the paucity of algal species.

The genus Plectonema is described by Prescott (1951) as becoming yellow

 

or brown with age. The mat of algae in the artificial streams turned to

a drab yellow-brown color sometime after _P. Boryanum became dominant.
Nitrogen at that time was at a low concentration. New growth of this

algal mat was a dark green color and was apparent in numerous tufts

about the periphyton mat and on the artificial substrates. This aging
process has been described by Kingsbury (1956) and Odum and Hoskin (1957)-

for Plectonema nostocorum Bornet ex Gomont. Kingsbury (_op. pit.)

 

decided the yellowing condition resulted from a depletion of nitrogen in
the medium and believed photosynthesis to be stopped or much reduced
in the yellow state. Odum and Hoskin (3p. _c_i_t.) reported that photo—
synthesis did not cease entirely when the yellow-brown condition was

present. The magnitude of gas exchange in this study also indicated that

50

photosynthesis by _1_3 Boryanum in the yellow—brown stage did not cease
entirely. The absorbancy spectrum of new growths of 1:. Boryanum is
given in Figure 8 and the peaks agree well with those givenby Kingsbury

(1956) for the pigments present in healthy _P nostocorum.

 

51

Figure 8. Absorbancy spectrum of 95% ethanol extract of
Plectonema Boryanum Gomont.

 

Percent Transmittanc e

10

20

30

40

50

60

70

80

90

100

52

 

 

680

_D/O/O\. e 9
O
O
_ O O
I I I I I 1 T
400 440 480 520 560 600 640
Wavelength (mp)
Pigment wavelengths).< 450
Chlorophyll 3: 430, 660 B carotene 480
C-PhYCocYanin: 615. 650 Myxoxanthophyll 490
Myxoxanthln 5 20
Figure 8

"‘Kingsbury, 1956

RESU LTS AND DISCUSSION

Effects of Study Conditions

Temperature

 

The effect of water temperature on the rate of primary production
was determined by creating a temperature difference of 5. 6 C between
the two artificial streams, holding other characteristics equal, and
comparing the net productivity of the two streams. Stream 2 was
maintained at the higher temperature (25.6 C) and was expected to have
the higher rate of production. An increase in temperature, at least up
to an Optimum, will increase most metabolic processes, but not all
at the same rate.

The results of most temperature studies have been reported in
terms of Van't Hoff’s quotient (Q10), the number of times that the rate
of a process increases with a 10 C rise in temperature. The Q10 value
generally accepted for photosynthesis is about 2. 0 while the range for
respiration is about 2. 0 to 2. 5. Most enzymatic reactions have a Q10
of 1.4 to 2.0. Several authors have reported Q10 values for algae in
the same approximate temperature range as was used in this study.
Osterhout andHaas (1918b) found Q10 values for I_J:lv_a of 1.69 for photo-
synthesis and 2. 04 for respiration. Van der Paauw (1934) studied
several green algae and reported, at 15 to 25 C, a Q10 range of 1.7 to
2. 1 for carbon dioxide assimilation and a range of 1. 7 to 2.4 for
respiration. Talling (1955) reported a Q10 of 2.3 for the growth rate of
a planktonic diatom and a Q10 of 2. 2 was given for photosynthesis by

freshwater phytoplankton by Ichimura and Aruga (1958).

53

54

Measurements by carbon dioxide and substrates revealed the
net production to be highest in the warmer water of stream 2, while
oxygen measurements showed the opposite (Figure 9). Statistical
analysis of the values in Figure 9, using a one-tailed Student's "t" test
for matched pairs, indicated no significant difference between pro-
duction at the higher temperature and production at the lower tempera-
ture at the 5% level; however, the higher temperature production was
significantly greater at the 10% level (t = 1. 537 > t.90 = 1.48, df = 5).
The mean estimates of net productivity in g cal :11"2 day"1 for
the two temperatures were used to calculate the Q10 value. -A logarithmic
relationship was assumed and the following formula was used.

10
p .—
Q10 = (Eight-ta

where P1 = 715.1, the productivity at temperature t1 (25.55 C) and
P; = 595. 7, the productivity at temperature t; (20. 0 C). Thus
Q10 = 1. 201’801 = 1.4. A value of 1.4 for net productivity indicates that
respiration increased approximately the same as or slightly more than
photosynthesis. The effect was probably due to an increase in
enzymatic reaction rates.

The average net productivity or rate of energy transfer for the
two streams was 595.7 g cal m'z day‘1 for stream 1 and 715.1 g cal
m'z day‘1 for stream 2. Gross productivity for stream 1 was 1451.0

g cal m"Z day ‘1 and for stream 2 was 1735.4 g cal m-z day'l.

Photoperiod

 

The effects of the length of photoperiod on primary productivity
were investigated by maintaining the lights of stream 1 on a "four hours
on - four hours off" basis while the lights of stream 2 were on continu-

ously for 12 hours and off for 12 hours. Thus both streams received

55

Figure 9. The effect of temperature on net production in
artificial streams as measured by carbon
dioxide, oxygen, and substrates.

Production in organic weight

 

Stream 1 (20 C)

56

Substrates

 

Stream 2 (25.6 C)

co,

 

Substrates

 

 

u—1

Weeks

Figure 9

4.1

57

the same amount of radiant energy daily, (but at different intervals.
Black crepe paper was draped over the streams to isolate the photo-
periodconditions. Other physical andchemical characteristics of the
two streams were equal.

- It is known that energy fixation by photosynthesis is more
efficient under conditions of flashing'light than during continuous light.
This is due to the occurrence of certain dark reactions. -It is doubtful
that dark reactions, which enhance production under flashing light,
would be important enough to influence the production rate under the
conditions of this study. However, Steeman-Nielsen. (1960) has shown
with C14 studies that l to 3% of light saturation fixation occurs in the
dark if the period is about four hours. Apparently the dark fixation is
rapid immediately after the lights go off and then declines. If this is
the case one might expect some increase in productivity by breaking
up the daily dark period even if only into three of four intervals.

The results of the photoperiod study are given in‘Figure 10.
Measurements by carbon dioxide and substrates show production to be
slightly higher under the divided photoperiod of stream 1. Oxygen
measurements were approximately equal for the two streams. The
data of Figure 10 were subjected to a one-tailed matched pairs test.
The analysis showed no significant difference at the 5% level between
the productivity of stream 1 and that of stream 2 (P = . 30). The
statistical analysis suggests that little effect can be at attributed to the
length of photoperiod as long as the daily quantity of light received is
equal for both streams.

The mean rate of net energy transfer for stream 1 was 691. 3 g
cal m"7‘ day"1 and for stream 2 the same rate was 649. 9 g cal In"2 day‘l.
The gross energy transfer for streams 1 and 2 was 2222. 1 and 2005.6

g cal rn'Z day"l respectively.

58

Figure 10. The effect of photoperiod on net production in
artificial streams as measured by carbon
dioxide, oxygen, and substrates.

Production in organic weight g m'?‘

8 In“?

 

59

Stream 2
(12 hrs. on - 12 hrs. off)

 

 

 

CO;
02
A Substrates
W I f
Stream 1
(4 hrs. on - 4 hrs. off)
CO;
02
A
Substrates
A E
I I W
1 2 4
Weeks

Figure 10

60

Light Intensity

 

The light intensity provided for the two streams was changed from
the standard conditions so a difference of over two-fold existed between
the streams. The effect of the difference in light intensity was then
determined. Stream 1 received the lower incident intensity of 63, 000
g cal m"Z day"1 (120 ft-c) provided by 100 watt bulbs suspended about
17 inches above the stream bottom. Stream 2 received 136, 800 g cal
m'2 day"1 (276 ft-c) from 150 watt-bulbs suspended about 12. 5 inches
above the stream bottom. The incident energy was slightly greater in
the pool areas of both streams since the lights were lowered to
compensate for water depth.

The radiant energy received by stream 2 was about 1% of the
average daylight value (1.92 g cal cm‘Z min“) and about 12% of the
optimum photosynthetic value of 0. 1 to 0. 15 1y min'1 (720, 000 to
1,080, 000 g cal rn-z day-1) given by Strickland (1960). Ichimura and
Aruga (1958) noted that light saturation values varied with the major
groups of algae, being highest for blue-greens, but at the same time
light saturation was at a low of 372 ft-c when influenced by oligotrophic
waters. » Kratz and Meyer (1955) reported growth rates to increase
rapidly when light was increased from 100 to 180 ft-c and to increase
more slowly when light was further increased to 260 ft-c. VA report on
Chlorella cultures by Myers (1946) gave 35 ft-c as the intensity for the
greatest photosynthetic capacity, probably referring to efficiencies,
and 100 ft-c as the intensity for the greatest growth rate. It is apparent
from these reports in the literature that the effect of the range of
radiant energy used in this study should result in an increase in pro-
ductivity under the higher energy rate.

The difference in production attributed to light intensity is given
in Figure 11. Measurements by carbon dioxide and oxygen show pro-

duction to be higher under the higher light intensity of stream 2.

61

Figure 11. The effect of light intensity on net production in
artificial streams as measured by carbon
dioxide, oxygen, and substrates.

In in

Production in organic weight

8 m‘?‘

 

 

62

Stream 2
(136,800 g cal m-Z day-1) CO;

/9/¥ubstrates

l I j T
1 Z 3 4

Stream 1
(63,000 g cal m-Z day-1) CO?-
02
Substrates

 

fi
—-(

Weeks

Figure 11

63.

Datafrom substrates show little difference between the twostreams.
The productionof stream 2 was significantly greater than that of
streamrl-at the-2. 5% level as demonstrated by a one-tailed matched
pairs test (t = 2.674 > 6975 = 2.571, df = 5).

The net productivity of stream 1 was 869. 9 g cal rn-z day"1 and
of stream 2 was 1259. 5 g cal m"Z day-1. Gross productivity of
stream 1 was 2504.4 g cal m-z day"l compared to 3380. 5 g cal rn"z
day"1 for stream 2.

rSince only two light intensities were used it is not possible-to
indicate whether the relationship of light intensity to productivity is
linear 'or-hyperbolic as discussed by Strickland (1960); however, con-
sidering the low light intensities "of this study relative to saturation
values in the literature, it might be assumed that the relationhere is

linear .

Current Velocity

 

The effect of flowing water on productivity and on other biological
phenomena is one of the major differences between streams and lakes.
The belief that water movement does influence productivity, directly
or indirectly, is one of the main objections against using the‘L-D bottle
method to measure the production of flowing waters. Reports that
flowing water enhances production have beenlargely limited to recent
years. Earlier reports were mostly secondary observations such as
that made by Butcher (1946), who noted that the number of algal cells
per squaremillimeter of glass slide was higher where the current was
fast than where it was slow. Gessner and Pannier (1958) studied the
respiration of Anabaena in Warburg flasks and learned that maximum
respiration was reached at a much lower oxygen tension when the flasks
were agitated than when the flasks were still. Some recent studies

have been specifically directed at determining the current effect.

64

Whitford (1960) theorized that an increase in current produced a steeper
diffusion gradient thus facilitating a better exchange of materials
between the cells and the environment. Whitford and~Schumacher'(1961)
reported that carbon dioxide evolution by algae was 70% greater in
current than in still water. Rawstron (1961) collected evidence showing
that the growth rate of periphyton on artificial substrates was greater
in riffles than in pools in the Red Cedar River.

- Evidence of the effect of flow on productivity was acquired in two
ways in this study. Both streams had a riffle and a pool area where the
velocity of flow differed. Under standard conditions the velocity of the
pools was 0. 5 cm sec"1 while the riffle velocity was 2. 5 cm sec'l.
-Comparisons of growth on artificial substrates at the different stations
was used to indicate any effect of the current. The velocity of flow over
the surface of the substrates in the riffle area was actually greater
than the riffle area in general since the substrate thickness reduced the
average water depth. The velocity of water over the substrates was
approximately 3.4 cm sec"1 rather than the 2. 5 cm sec"1 in the general
riffle area.

The dry weight of periphyton collected on artificial substrates
was used to measure the effect of current on production. Substrates
were located at all five stations in both streams and data from all studies
were included in the results. . Stations 1 and 2 represent the riffle areas
and stations 3 and 4 are from the pools. (Station 5 is not representative
of either area since light intensity at station 5 was less than the other
stations. The dry weights from the five stations were subjected to a
one-way analysis of variance and the results, given in Table 6, show
the production of stations to be significantly different at the 5% level.
Kramer's modification (1956) of Tukey's multiple range test revealed
the production of stations 1 and 2 to be significantly different from the

remaining stations in both streams. Stations 1 and 2 were not significantly

65

Table 6. Analysis of variance of production in dry weight at the five
stations of streams 1 and 2.

 

 

 

 

 

 

Stream 1
Source of Sum of Mean
Variation Squares df Square F Ratio
. _ 13, 086.39 __
Stations 52,345.55 4 13,086.39 F — 1,301.54 — 10.054
Within 206, 944. 30 159 l, 301. 54 F.95(4, 159) = 2.43
Total 259, 289. 85 163
Station means in milligram dry weight per substrate:
_1__ ._E_ .3... .4— __5__.
49.21 56.18 23.96 20.11 8.92

Kramer's multiple range test reveals stations 1 and 2 to be significantly
different from stations 3, 4, and 5, but not from each other.

--—-----—m~ma-m—_~“mum-‘dmu-muI—m—am—umn~—-neflmwa-m‘~----umu_-wn-_--m——

Stream 2

 

 

 

 

 

Source of Sum of Mean
Variation Squares df Square ‘F Ratio
. _ 14, 570.04 _

Stations 58,280.18 4 14,570.04 F — 1,538.94 — 9.467
Within 238,535.35 155 1,538.94 F.95(4,155) = 2.43
Total 296, 815. 53 159
Station means in milligrams dry weight per substrate:

_1_ __Z__ .3... _fi*_ __5__

60.94 50.08 24.91 21.43 9.07

Kramer's multiple range test reveals stations 1 and 2 to be significantly
different from stations 3, 4, and 5, but not from each other.

 

66

different from each other and stations 3, 4, and 5 were not significantly
different from one another.

Before the higher production of the riffle areas can be attributed
entirely to current effect it is necessary to rule out the effects of
nutrients and light intensity. Light measurements and calculations
showed that the light intensity at the substrate surfaces, although not
constant for all studies, was slightly greater in the pool than in the riffle
areas. This was a result of placing the lights slightly nearer the stream
bottom in the pool areas to compensate for the greater water depth to be
penetrated by the light waves. It is assumed that the slight difference
in light quality reaching the substrates as a result of the different water
depths did not influence production enough to alter the conclusions.

Water samples for nutrient analysis were ordinarily taken from
only one site in the streams; however, on a few occasions samples for
phosphorus were taken from riffle and pool sites to determine if upstream
periphyton was receiving the benefit of greater phosphorus concentrations.
The results of eight paired samples from each stream for total phosphorus
were analyzed by a two-tailed matched pairs test. Results indicated no
significant difference at the 5% level between the phosphorus concentra-
tions of riffle and pool sites in either stream (stream 1: P = .10,
stream 2: P = . 30). It is thus assumed that phosphorus concentrations
did not influence production in the riffle sites more than in the pool- sites.

Since the phosphorus concentration was as low as any other major
nutrient, it is assumed that the concentrations of other nutrients did not
decrease enough downstream to limit production in the pool. The higher
production of the upstream riffle areas is thus attributed to greater cur-
rent velocity.

Other evidence that water velocity influences production was
collected in a manner similar to those described for the first studies.

The gradient of the two streams was changed so stream 1 had a velocity

67

faster than the standard conditions and the velocity of stream 2 was

slower than standard conditions (Table 5). -Production was measured

by carbon dioxide, oxygen, and substrates and all three methods

demonstrated higher production in the faster stream'(Figure 12). The

data were analyzed using a one-tailed matched pairs test and the results

indicated that production in stream 1 was greater than production in

stream 2 at the 5% level of significance (t = 2. 295 > t.95 = 2.015, df = 5).
The mean net and gross productivity in g cal m'z day'1 for

stream 1 were 1994. 2 and 6026. 5 respectively while the same productivity

values for stream 2 were 1485. 3 and 4356. 5.

Chelate

Ethylene diamine tetra-acetic acid (EDTA) was used to determine
the effects of organic chelation on primary productivity. The action of
chelates is due to a strong affinity of the organic molecules for poly-
valent metallic ions. When EDTA is added to a nutrient medium, poly—
valent metallic ions such as iron, magnesium, and calcium are complexed
with the chelate. The basis for suspecting an increase in productivity
when chelates are added is that certain insoluble nutrients, required for
algal growth, are complexed and brought into solution, while other
nutrients tied to the insoluble forms are then indirectly released into
solution. This applies to iron and phosphorus. When iron is oxidized
from the ferrous to the ferric state, as occurs in oxygenated water, it
becomes insoluble and when phosphate is present the two elements pre-
cipitate as insoluble ferric phosphate (Hutchinson, 1957). It has been
demonstrated that ferric iron precipitated in bottom muds can be brought
into solution by complexing with an added chelate (Schelske, 1962).

When the ferric phosphate bond is broken the soluble phosphate ion is
freed. Both iron and phosphorus are necessary for the growth of algae.

In this study phosphorus availability was emphasized although it is

68

Figure 12. The effect of current velocity on net production
in artificial streams as measured by carbon
dioxide, oxygen, and substrates.

.g m‘z'

Production in organic weight

8 m""'

14‘

12-

10-

 

20—

18‘

16‘

14‘

12‘

10‘

Stream 2

(Slow)

69

CO2

Substrates

 

Stream 1

(Fast)

‘

—

—

coz

Substrates

 

 

Weeks

Figure 12

 

70

assumed that any increase in productivity could be attributed to in-
crease in available iron as well as to phosphorus, since algae have
the capacity to use chelated iron. It has been speculated that many
metallic nutrients are complexed in aquatic systems by naturally
occurring organic chelates. Fogg and Westlake (1955) stated that the
large amounts of cellular products, lost or secreted by blue-green
algae, may act as chelates.

The effect of chelate additions on the phosphorus concentrations
of the artificial streams was investigated during the first year when
the streams were being colonized and established. , EDTA was added to
each stream at a concentration of 40 mg liter‘l. Soluble phosphorus
concentrations were then compared to prechelate concentrations.

The response to the chelate was indicated by a rapid rise in the: soluble
phosphorus concentration of both streams (Figure 13). At the end of

56 hours the total soluble phosphorus release in streams 1 and 2 was
25.83 mg and 32.47 mg respectively. The source of the released
phosphorus was assumed to be from previously precipitated compounds
of iron and other metallic elements, possibly calcium or magnesium.

It is evident that the chelate effect on phosphorus release was significant.

The effect of EDTA on the primary productivity of the artificial
streams was studied approximately 16 months later. The chelate was
again added to both streams, but stream 2 received a concentration of

30 mg liter'1 and stream 1, 10 mg liter-1.

It was expected that stream 2
would show a higher productivity than stream 1. All methods of estimat-
ing productivity confirmed the expectation (Figure 14). The production
values were submitted to a matched pairs analysis using a one-tailed
test. The results of the statistical analysis indicated that production in
stream 2 was greater than in stream 1 at the 2.5% level of significance

(t = 2.876 > t,975 = 2. 365, df = 7). The mean net and gross productivity

in g cal rn'Z day‘1 for stream 1 were 612 and 1636 respectively and for

stream 2 were 1096 and 2236 respectively.

71

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73

Figure 14. The effect of a chelate on net production in
artificial streams as measured by carbon
dioxide, oxygen, and substrates.

8 In"?

Production in organic weight

8 m'2

Stream 1

(Low chelate)

74

/ / Substrates

 

 

 

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1

Stream 2

(High chelate)

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Figure 14

 

75

The water-chemistry, in Figures 6 and 7, revealed that alkalinity
in stream 2 increased while that of stream-1 decreased. The phosphorus
concentration in both streams increased, but slightly more inrstreamrl.
Thus the higher productivity in stream 2 cannot be accounted for on the
basis of phosphorus release, but is probably due to some unmeasured
relationship. It is possible that a limiting metallic ion, less readily
chelated,e. g. ,1 Mn or Mg, was complexed by the higher chelate concen-

tration in stream 2.

Primary Productivity

The three methods used to measure primary production were the
uptake of carbon dioxide, the evolution of oxygen, and biomass collected
on artificial substrates. Three methods were used for two reasons:

1) as a combined effort to better indicate the effects of various environ-
mental factors as already shown, and 2) as a means of comparing and
evaluating the methods in an effort to determine the method best suited

for use in flowing waters.

Growth Rates on Artificial Substrates

 

The use of artificial substrates to collect periphyton as a measure
of primary production has only been considered in recent years.
Fortunately most of the recent reports about artificial substrates have
contributed important information concerning their use. . Newcombe
(1950) reported that the percent of organic matter was greater for algae
from the undersides of slides because of the silt that settled on the tops.
Newcombe (1949) also noted that periphyton on slides was representative
of the natural population, but Lund and Talling (1957) theorized that
slides would have to favor the pioneer species of the community. ~Peters

(1959) investigated this subject and reported, like'Newcombe (1949),

76

that slides were not selective. Castenholz (1960) also stated-slides
to be non-selective.

One of the most important and difficult questions yet to be
answered is what substrate exposure time gives the most representa-
tive sample of periphyton. Most investigators using artificial sub-
strates have selected a time period that allowed a perceptibly good
coating of periphyton to‘accrue on the substrate. This period is
usually reported as being between 10 days and four weeks and is practical,
but does not: answer the question. Two questions arise to be‘answered
before an adequate answer to the first question can be determined.

In what part of the population growth pattern is the periphyton on
artificial substrates? And does this phase of growth on the artificial
substrates represent the over-all condition on the stream bottom where
the periphyton is usually in all combinations of the growth pattern?

An attempt to answer these questions was made by studying the
accrual of periphyton on substrates in the artificial streams.
Substrates were removed every 2 or 3 days up to 34 days. It was thus
possible to determine the colonization period and to follow the subse-
quent rates of growth. Lund and Talling (1957) maintain that the com-
plexity of environments makes attempts to use mathematical models
to describe the population growth of algae unprofitable. .Control of
the environment in the artificial streams and the great predominance
of one algal species avoided some of the complexities found in natural
ecosystems.

The question involving the pattern of growth on the bottom of the
streams was investigated indirectly. The rate of periphyton growth
on the substrates was compared to rates measured by the pH-carbon
dioxide method. .Both methods measure net production; however, the
carbon dioxide method measures the net production of the entire com—

munity thus affording a comparison of growth on substrates with growth

77

of the long established population on the stream bottom. This would
rarely be feasible in natural systems since the carbon dioxide method
would include the changes caused by the metabolism of faxiha and
higher aquatic plants which were absent in the artificial streams.

The study of growth rate was incorporated with the study of
current velocity and results reflect different growth rates for the two
streams. The data indicate that growth on substrates follows the
sigmoid pattern at least into the logarithmic phase (Figure 15).
Inspection of the substrates revealed the first periphyton to become
measurable no earlier than three days and this period of time was
subtracted from the exposure periods of the shingles for the growth
rate study. Thus in Figure 15, day 0 corresponds to day 3 making an
initial 3 days of no standing crop which does not appear on the graph.
This initial period is required for establishment of the periphyton
on the substrate and should not be included in calculations of productivity.

The sigmoid growth curve can be divided into three sections, the
initial slope being the lag phase, the steep slope being the logarithmic
phase, and the final slope approaching the asymptote being the senescent
phase. When the data were plotted on a logarithmic scale the lag phase
and logarithmic phase became obvious (Figure 16). The lag phase
extended through approximately 12 days in stream 1 and about 13 to 14
days in the slower current of stream 2. The data were converted to
productivity values and plotted by riffle and pool in Figures 17 and 18.
The data fit the typical growth rate curves and indicate in both riffles
and pools that the periphyton on the shingles at 34 days is at or near the
maximum rate and further samples would probably have continued at
the same rate or would have shown a decline. This decline would be
the senescent phase and would continue on the lines of Figure 15 reaching
the asymptote in about another 30 days. Generally the periphyton coat-

ing on the artificial substrates begins to slough off before it proceeds far

78

Figure 15. Biomass of periphyton on substrates exposed for
various time periods in the artificial streams.

Standing crop in dry weight (g m'z)

l4

 

79

H Stream 1 (Fast)

A-"A Stream 2 (Slow)

 

 

Time of substrate exposure (days)

Figure 15

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86

into the senescent phase. When sloughing off of the periphyton is con-
sidered as part of the growth pattern then the curve has the J-s‘hape
growth form. Odum (1959) describes a population of the J-shaped form
as dropping directly back to an initial level when the population density
reaches some limiting level before the asymptote. This may well be the
situation for periphyton mats, at least of the form as that in the artificial
streams, i. e. , a blue-green algae with a gelatinous matrix. Thelimit-
ing factors may be a lack of space and light as the upper layers of
periphyton "shade out" the underlying filaments adhering to the substrate
and cause the death and subsequent loosening of the algae. Another
possibility may be as the mat becomes thicker, gas is unable to diffuse
through the mat and bubbles are formed which loosen the periphyton.

The growth form of the algae in the artificial streams was further

identified by calculation of the growth constant, k, in the exponential

equation
Pt = P0 ekt
where Pt 2 the standing crop at time t,
P0 = the standing crOp at time 0,
t = the time in days,
and e = the base of natural logarithms.

Calculations were based on values taken from Figure 15. During the
current velocity study the growth constant for the logarithmic phase of
stream 1 was 0.0692 and for stream 2, k = 0.0676. McCombie‘(1960)
studied cultures of green algae and reported a range for k of 0.02 to 0. 1
under a temperature range of 5 to 25 C and a light range of 150 to 200
ft-c. ‘Riley (1941) reported k = O. 345 for plankton growth on Georges
Bank when productivity was 1 g m“2 day“1 dry weight. The productivity
for the artificial streams was roughly 0.3 g m-2 day-1 dry weight for

the period used to calculate the growth constants.

87

The turnover rate and turnover time for biomass were also calcu-
lated for both streams for the current velocity study. Turnover rate
is defined as the fraction of the total amount of algae in the ecosystem
which is produced in a given time period (Odum and‘Odum, 1955).
The turnover time is the reciprocal of the turnover rate or the time
necessary to produce an amount of algae equal to the standing crop.
Standing crop for both streams was estimated to be about 11. 0 grams
of ash-free dry weight per square meter. The productivity for stream 1

was estimated as O. 367 g m‘2 day“l ash-free dry weight.

. 367 g m'2 day-1

 

 

_ _ -1 -1
Turnover Rate — 11 g m_2 — 0.0333 day (3. 33% day )
l
Turnover Time = 0333 = 2.9. 97 days or 12. 2 turnovers year'1

The same calculations for stream 2. were:

.314

 

Turnover Rate = —T1— = 0.0285 day”1 (2.85% day-l)
. 1 1
Turnover Time = 0285 = 35.09 days or 10.4 turnovers year-

Comparisons between productivity rates as measured by substrates
and by carbon dioxide reveal the rates by substrates to be consistently
lower during the studies of effects of environmental factors. A review
of Figure 15 shows that the rate of production (standing crop divided
by exposure time) increases with increasing exposure time. Seemingly
then, the best estimates of productivity are made from data from sub-
strates with the longest exposure times. This is logical since the
periphyton on the substrates exposed longest more nearly parallel the
algae on the stream bottom. Moreover, the periphyton growth rate on
the substrates most similar to that on the stream bottom is that growth
rate occurring toward the end of the exposure period. Therefore if the

productivity is calculated for the growth occurring during the last three

88

days of a30 day substrate exposure period, the estimate should approach
that based on the periphyton of the stream, provided the algae of the two
sites are in comparable phases of the growth pattern. During the
current velocity study, substrate pairs were removed at frequent
intervals thus allowing subtraction of the growth of one periodfrom that
of a longer period.

Measurements for carbon dioxide at 28 days during the current
velocity study yielded net productivity values of 0.403 g In"2 day"l organic
weight for stream 1 and O. 359 g m“; day"1 for stream 2 (Figure 12).
Carbon dioxide values are low since respiration in the reservoirs is
included. Substrate data from' Figure 15 for a 28 day exposure timeyield
productivity values in g m"2 day"1 organic weight for streams 1 and 2 of
O. 327 and 0. 250 respectively. When the standing crop at day 25 is sub-
tracted from the standing crop at day 28 and productivity calculated for
the intervening 3 days, the results for streams l and 2 are increased
to 0.424 and 0. 326 g m”2 day“l respectively thus becoming closer to the
estimates by the carbon dioxide method.

The collection of periphyton on artificial substrates appears to
provide a good means of estimating primary productivity when the
exposure period is long enough to allow the collected periphyton to
approach a growth phase similar to that of the periphyton on the stream
bottom. The most valid estimates are obtained when calculations are
based on growth accrued during the last few days of the exposure period.
Productivity based upon substrate data does not include any production by

higher aquatic plants.

Diurnal Gas Change 3

 

The comparison of productivity values estimated from oxygen and
carbon dioxide data was preceded by a number of preliminary calcu-

lations and assumptions. Before oxygen and carbon dioxide methods

89

can be compared the data must be converted into some common unit.
Since measurements also included biomass it was decided to convert
all values to ashefree dry weight. - Conversion of gas measurements
to organic weight requires a knowledge of or assumptions concerning
the photosynthetic product. Many investigators have in the past
assumed the organic matter produced to be entirely carbohydrates.
This assumption may be warranted in view of the other errors involved,
but at the same time the fullest use should be made of available infor-
mation. Myers and Cramer (1947) stated that in growing cultures of
Chlorella as much protein was synthesized as carbohydrate. Moyse
(1959) also reported that materials other than carbohydrates were
synthesized during photosynthesis and noted rapid production of amino
acids during low light intensity.

Estimations of the composition of the algae produced in the artificial
streams were based on measurements of the nitrogen content of the algae,
on the caloric values of the algae, and on reports of the fat content of
blue-green algae. The mean organic nitrogen, based on 62 Kjeldahl
determinations made throughout the investigation, was calculated as
0.0381 mg N per mg dry weight of algae. This value times the conven-
tional factor of 6. 25 indicated the algae to be 24% protein. The blue-
green algae are reported to have a low lipid content, 4% of the dry
weight in one case (Strickland, 1960). The mean caloric value, based

on 31 determinations, was calculated as 4520 cal g"1

of dry weight of
algae. Using values of 9500, 5700, and 4000 calories for fat, protein,
and carbohydrates respectively, the composition of the algae was
determined as 76% carbohydrate, 21% protein, and 3% lipid. This
composition gives a caloric value of 4522 calories.

Synthesis of protein indicates the photosynthetic quotient (PQ) may
be greater than 1.0. Strickland (1960) discusses PQ values and notes

that when nitrate is the source of nitrogen for protein synthesis the PQ

90

may be as high as 1.6. Ryther (1956) gave a PO of 1.45 when nitrate
was the nitrogen source and cited an average PD of 1. 2. Odum-“(1957a)
also noted ‘PQ values from 1. 2 to l. 38 when protein synthesis was high.
Metabolism of the oxygen from the nitrate molecule produces ahigh PC)
by increasing the oxygen change of the photosynthetic process (+ A 02/
- A C03). -Nitrate was the usual source of nitrogen in the artificial
streams. On one occasion NH4NO3 was used; however, the long term
source was recycled nitrogen which would be in the form of nitrate since
the stream waters were always high in dissolved oxygen. The respiratory
quotient (RQ) is the inverse of the PQ and is influenced by the same
factors, but during the day photosynthesis was greater than respiration
thus it is reasonable to correct gas values with the PO. A P0 of 1.0
would indicate an uptake of 6 moles of carbon dioxide, production of 1 mole
of carbohydrate, and evolution of 6 moles of oxygen. PQ values were
estimated for this study on the basis of literature values and measured
caloric values; assuming the caloric values to be an indication of the
amount of protein synthesis. The highest caloric values indicated only
moderate protein synthesis thus a PO of l. 3, somewhat less than the
quoted literature values, was assumed. Intermediate and low caloric
values, still above the carbohydrate level, were assumed to be repre-
sented by a‘PQ of l. 2 and 1. 1 respectively. These PQ values were used
to determine factors to convert oxygen and carbon dioxide measurements
to organic weights.

The organic product of photosynthesis was assumed to have a
molecular weight of 180. rAlthough this is the same molecular weight
as glucose, it was derived on a different basis. Amino acids in general
have a molecular weight less than glucose, but fatty acids have a molecu-
lar weight higher than glucose. It was assumed that the opposing effects
of amino acids and fatty acids would result in little influence on the

molecular weight of the carbohydrate component (76%). If 6 moles of

91

carbon dioxide were used to synthesize 180 g'(1 mole) of organic matter,
then axPQ of l. 2 would result in the production of 7. 2 moles of oxygen.
To place the gases on an organic weight basis, the grams of carbon
dioxide were multiplied by 0.682 (1 mole/6moles = 180 g/ 264 g = .682)
and with aPQ of l. 2 the grams of oxygen were multiplied by a factor of
0.782 (1 mole/7.2 moles = 180 g/230 g = .782). For PQ's of 1.1 and

l. 3, the factors for oxygen were 0. 852 and 0. 720 respectively.

Measurements of net productivity by oxygen, carbon dioxide, and
periphyton collected on substrates are given in Table 7. The-oxygen
values are corrected for respiration and BOD in the filter boxes and
reservoirs thus giving a measurement of productivity for the entire
system as does the carbon dioxide data. The substrate data represent
net production only for the area of the stream under the lights and thus
the differences between the substrate estimates and the gas estimates
is even greater than shown.

A two-tailed matched pairs test was used to test if results by the
oxygen method in Table 7 were different from results by the carbon
dioxide method. The test indicated that the methods are not significantly
different at the 5% level (P = . 60). Frey and Stahl (1958) reported
general agreement among measurements of productivity by oxygen,
carbon dioxide, and C14 methods using the L-D bottle technique. Odum
(1957a) also reported similar results between i_r_1_ s_i£1_1_ oxygen and carbon
dioxide measurements when results were corrected by a photosynthetic
quotient.

According to theory the oxygen method and carbon dioxide method
should produce the same estimates and this is suggested by the statisti-
cal analysis. The differences that do exist between individual estimates
in Table 7 may be due to false assumptions and errors inherent in the

methods .

92

 

 

 

 

 

Table 7. Comparison of net productivity in g m'2 day"l organic Weight
as measured by the oxygen, carbon dioxide, andsubstrate
methods.

Carbon- Dioxide Substrate
Stream , Oxygen AMethod Method Method
Study PQ ‘No. 0; ‘ ‘org. wt. COZ org. wt. org. wt.
Eifpera‘ 1, 3 1 .109 .078 .227 .155 .088
2 .077 .055 .246 .168 1. 189
1 .182 .131 .176 .120 .044
2 .128 .092 .292 .199 .180
Photo-
period 1.3 l .158 . 114 .248 .169 .070
1 .174 .125 .213 .145
2 .108 .078 .255 .174 .037
2 .261 .188 .194 .132
1 .238 . 171 .406 .277 .053
2 .263 .189 .313 .213 .046
Light
Intensity 1. 2 1 . 206 .161 . 208 .142 . 042
2 .310 .242 .352 .240 .039
1 .239 .187 .318 .217 .052
2 .341 .267 .403 .275 .043
Current 1.1 1 .704 .600 .573 .391 .294
1.2 2 .535 .418 .558 .381 .241
1.1 1 .854 .728 .591 .403 .317
1.2 2 .467 .365 .527 .359 .231
Chelate 1.2 1 .222 . 174 . 306 .209 .098
2 .380 .297 .289 .198 .373
1 .108 .084 .226 . 154 .090
2 .197 .154 .340 .232 .326
1 .205 .160 .234 .160
2 .171 .134 .410 .280

 

93

The formation of gas bubbles under the mat of algae occurred
daily; Odum (1957a) claimed that gas in bubbles formed among aufwuchs
was not all oxygen because the bubbles remained unchanged at night.

The bubbles formed in the artificial streams deflated at night and re-
appeared during the next day. This phenomenon indicated the gas in

the bubbles to be prirnariily oxygen. rAlthough the oxygen of the bubbles
would theoretically be replaced by carbon dioxide at night, the carbon
dioxide would tend to diffuse more readily into and through the moist
periphyton mat because of the high solubility of carbon dioxide. If the
gas of the bubbles is mostly oxygen then measurements by the oxygen
method would be lower than the carbon dioxide measurements which was
the general case, except for the current study, as shownin Table 7.

Diffusion correction is another critical point in estimating pro-
ductivity by the gas methods. Burr (1941) noted that carbon dioxide
diffused into water 25 times as fast as oxygen, but that oxygen was 700
times as concentrated in air resulting in a net oxygen diffusion 28 times
that of carbon dioxide. Thus corrections for oxygen are more critical
than for carbon dioxide. The gas transfer coefficients, in g O; m-2 hr'l,
assumed in this study were 0. 04 for the slow stream velocity, 0. 12
for the fast stream velocity, 0. 06 for the stream at 20.0 C, and 0.07
for the stream at 25.6 C and for the streams under standard conditions.
It is possible that the coefficient for the faster current is in error and
may account for the consistently higher oxygen values of the current
study (Table 7); however, the coefficient seems logical in view of the
temperature and current conditions.

Diffusion correction for carbon dioxide, although neglected in this
study, may be important under conditions of high pH and carbonate ion
concentration ((COZ entry) or low pH and high carbonic acid-carbon
dioxide concentration (COZ escape). Verduin (1956) calculates 26 mmoles
1

m"2 day" as the highest possible entry of carbon dioxide and in some

94

cases this would be significant. Cowles and‘Schwitalia(l923) observed
increases of 0. 1 pH unit where 'waterflowed over falls and rapids and
attributed this to loss of excess carbon dioxide by bubbling.

Since results by the two gas methods are in general agreement,
the best method for use in flowing water depends upon stream conditions.
The oxygen method requires special attention to obtain measurements
for calculation of a gas transfer coefficient, correction for bubbles if they
occur in any large amount, and determination of aNPQ value if results
are to be placed on a biomass or energy basis. Additional requirements
are given by Odum (1956). The pH-carbon dioxide method requires the
formation of conversion graphs from titration data for each estimate,
measurements of the alkalinity of the water, and corrections for diffusion
under certain conditions. The pH-carbon dioxide method appears to be
the simplest method, but it is limited in accuracy to the more poorly
buffered water or, more correctly, to waters yielding measurable pH

Changes.

Phytopigm ent Conc ent ration

 

The concentration of extracted phytopigment was not used to esti—
mate productivity since biomass determinations were also made on all
of the samples used for the pigment analysis. The data were collected
to determine if the phytopigment method could be used instead of the
biomass method. Both methods require the collection of periphyton on
artificial substrates; however, the time required for constant weight
determinations is much-longer than the time needed for extraction and
colorimetric readings of the phytopigment. If it can be shown that
phytopigment concentration has a definite and consistent relationship to
the organic weight and that this relationship can be easily determined

then pigment extraction would be the better method to use.

95

Grzenda and Brehmer (1960) and-Peters (1959) showed that a
.linear relationship existed between phytopigment and organic weight
for diatoms of the Red Cedar River, Michigan. -Peters (_. _.)
also reported that although a common slopecould be used, one regression
line could not be used for five different diatom communities. Peters
suggested that community differences caused a difference in the phyto—
pigment-organic weight relationship.

Several linear regressions were calculated and compared in this
study to see if differences existed in the phytopigment—organic weight
relationship of the artificial streams and also to compare the predictor
equations with those of other authors. The regression lines of organic
weight on phytopigment were calculated for streams l and 2 for the over-
all study, for the light intensity study, and for the current study.

The formula used for the regression model was

? = a + bx
where Y = the mean organic weight estimate in milligrams,
a = the intercept of the Y axis,
b = the point estimator of the population slope,

and X: the observed phytopigment reading in phytopigment units.
The coefficient of correlation, r, was also calculated for all regression
lines.

Calculation of regression equations for the light intensity study

revealed the following:

Streaml Stream 2
§=1.48+90.41X f=1.11+94.32x
Range ofX= .018 to.76 Range ofX= .02 to.51
n= 10 n= 10

r = .9795 > r3995 = .872 r = .9586 > 139,,5 = .872

96

An analysis of covariance indicated the slopes and intercepts to be not
significantly different at the 5% level (slopes: P‘= . 90, intercepts:
P = . 90) thus suggesting that one regressionline could be used for the

two streams. The common regression equation was

Y : 1.45 + 91.5X

for which r = .973 > r.9995 = .679.
The following equations and values were calculated for the current

velocity study.

Stream 1 Stream 2
§=O.2+84.57x §=-10.11+101.59x
Range of X = .005 to 2.16 Range of X = .02 to 1.46
n=60 n=66
r=.967 > r.9995=.414 r= .936 > r.9995=.414

An analysis of covariance for the two equations for the current velocity
study indicated that the slopes were significantly different at the . 5%
level. Thus a common slope was not calculated.

The combined data for all studies for streams 1 and 2 were sub—

jected to the same analysis.

Stream 1 Stream 2
Y=1.29+83.7X §=—4.40+90.2X
Range of X = .005 to 2.16 Range of X = .02 to 1.46
n = 89 n = 95
r = .969 > 17.9995 : .36]. r = .908 > 17.9995 : .36].

The analysis of covariance testing the regression lines of streams 1 and
2 showed no significant difference between the slopes or between the
intercepts at the 5% level (slopes: P = . 25, intercepts: P = .75). The
use of a common regressionline is suggested by these analyses and

calculations resulted in the equation

97

1? =1.34 + 86.08X

and a coefficient of correlation of
r»: .946 > r,9995 = . 324.

The slight difference that exists between slopes of the regression
lines for-the light intensity study may be due to the effect of the light
differences. . Sargent (1940) reported that Chlorella under high illumi-
nation had a lower chlorophyll content than under~low illumination.
Yentsch and Scagel- (1958) also reported higher pigment concentrations at
lower light intensities. The slope difference here also indicates a lower
pigment concentration under higher light intensity of stream 2;,however,
this difference in slopes persists even after the light intensity study
and may be due to some other effect.

The differences among the regression equations suggests that
various factors may influence the phytopigment-organic weight relation—
ship. -At the same time the agreement between the equations for streams
l and 2 based on the combined data of all studies indicates that these
factors, when operating or considered together, may counterbalance
one another. This may be a modification of the community homeostasis
discussed by Odum (1959) where combined environmental effects, rather
than combined species, produces more consistent results.

The regression equation given by Grzenda and Brehmer (1960)
is ’1? = -1. 72 + 82. 37X which agrees well with the common regression
line for this study ('1; = -1. 34 + 86.08). This agreement implies that a
consistent phytopigment-organic weight relationship may exist especially
when sufficient data from a variety of community and environmental types
are considered. If this is true one regression equation could be used to
estimate productivity by the phytopigment method with no more error
involved than exists in the other methods. Further evidence in the form
of regression equations based on studies in other aquatic ecosystems,

is needed to substantiate this hypothesis.

98

Energy Transfer and Efficiencies

The fixation of radiant energy by aquatic plants is one definition
of primary production and the use of energy terminology is the basic
and most meaningful way to present production data. . The energy
dynamics of a biological system, like those of physical systems, are
defined by the first and second laws of thermodynamics which are:

1) energy can be neither created nor'destroyed, and 2) energy changes
and transfers are accompanied by an increase in the entropy of the
system thus implying a degradation of the energy and efficiencies less
than 100%. These laws are the basis for the statement by MacFayden
(1948) that matter circulates, but energy passes through a biological
system only once. MacFayden (pp. _c_i_:c.) rightly suggested that the
terms "yield" and ”productivity” should be excluded from the field of
energy measurements. The term "energy transfer" is used here to
denote the absorption and fixation of radiant energy by algae.

» Estimation of the energy transferred by algae requires measure-
ments of the initial radiant energy impinging on the system and the
energy content of the final organic product. The initial radiant energy
was represented by two values, 1) the incident light at the surface of

the water, L and 2) the available light at the surface of the periphyton

i:
mat, La (Table 5). The energy content of the algae was determined in
calories by bomb calorimetry. The mean and standard deviation for all
measurements (n = 31) of caloric values were calculated as 4520 :1: 260

g cal. The conversion equation then is

g cal = g organic wt. x 4520 i 260.
Caloric measurements were made for duplicate samples and the mean
and standard deviation for the most variable andleast variable pair of
measurements were 4560 i 85 and 4945 :1: 7 g cal respectively. The

calories per gram of organic weight used for each study were as follows:

 

99

4923 g cal for the temperature study, photoperiod study, and-light
intensity study; 4320 g cal for stream 1 and 4498 g cal for stream 2
during the current study; and 4338 g cal for stream 1 and 4400 g cal
for stream 2 during the chelate study. These caloric values are the
means of calorimetric measurements of algae produced during each
particular study.

The conversion equation for dry weight to organic weight was
also determined. Based on 214 measurements, the mean and standard
deviation of the percent organic weight were calculated as 88. 8 :1: 7. 0
thus

mg organic weight = mg dry weight x .888 :L' .07.

Strickland (1960) estimated a conversion value for green algae of
. 85 21:...05 while Milner (1953) reported an ash content of 9. 35% for blue-
green algae and Schuette (1918) reported an ash content of 6. 52% also
for blue=green algae.

The energy transfer per square meter per day was calculated
for streams 1 and 2 for each study period (Table 8). The calculations
were made by multiplying the mean organic weight estimated by the
carbon dioxide and oxygen methods (Table 7) by the calories per gram
listed for the particular study. The amount of energy transferred by
the periphyton was similar for all studies except the current study when
daily nutrient supplements were added to the streams. This may indi-
cate that some nutrient was a limiting factor in the other studies, but
apparently not to the extent that the effects of the study characteristics
were suppressed. The nutrient may have become limiting only after other
limiting environmental factors were removed thus establishing an upper
boundary for energy fixation and also exemplifying the complexity of
biological systems. According to Van Oorschot (1955) low nitrogen
concentrations reduced the efficiency of algal cultures. This is apparent
in Table 8. When the energy source is constant, lower rates of energy

fixation result in lower efficiencies.

100

 

 

 

 

Table 8. Energy transfer and efficiencies for periphyton in streams
. Energy (g cal m72 day'l) Efficiencies (percent)

Study Number Li La Pg P1,1 :3 Pg .1311 £32

Tempera-

ture 68,200 48,240 1451 596 2.1 3.0 0.9 1 2
68,200 48,240 1735 715 2-5 3.6 1.0 1 5

Photo-

period 68, 200 48, 240 2222 691 3. 2 4. 6 l 0 1. 4
68,200 48,240 2006 650 2.9 4.2 1.0 1 3

Light

Intensity 63, 000 44, 200 2504 870 4. 0 5. 7 1 4 2. 0

136,800 95,000 3380 1260 2.5 3.6 0.9 1 3

Current 68,200 48, 240 6026 1994 8.8 12.5 2.9 4 1
68,200 48,240 4356 1485 6.4 9.0 2.2 3 1

Chelate 68,200 48,240 1636 612 2.4 3.4 0.9 1 3
68,200 48,240 2236 1096 3.3 4.6 1 6 2.3

35 67,160 47,432 2768 953 4.1 5. 1 4 2.0
81,920 57,592 2743 1041 3.3 4.8 1 3 1.8

Grand

Mean 74,540 52,512 2756 983 3.7 5.3 1 3 1.9

 

L.1 = incident light energy, 7L3 = available light energy,

Pg: gross energy transfer, P

Pn/I-Ii
pn/La :

I1

‘1 Production efficiency

= net energy transfer,

Tropic level energy intake efficiency or Lindeman's (1942)
efficiency or photosynthetic efficiency

101

The efficiencies of energy transfer often reveal information not
demonstrated by the energy transfer rates. Also comparisons with
other ecosystems, where theradiant energy is different, are best made
usingefficiencies. The efficiencies calculatedfor Table 8 are based
on those established in the literature. The progressive efficiency for
trophic levels, xn/an’ defined by Lindeman (1942) is represented for
primary producers by the ratio of gross energy transfer to incident or
available radiant energy (Pg/Li or'Pg/La respectively) (Odum, 1959).
The efficiencies given by the ratio of net energy transfer to incident
or available radiant energy (Pn/Li or Pn/La respectively) were used
by Juday (1940) and are represented by Odum (op. cit.) as Pt/Pt-l
(the trophic level production efficiency) where P is production of biomass
and t is a trophic level; t-l in the case of primary producers representing
the source of radiant energy. The efficiencies considered here to be
most representative of the ability of algae to transfer energy are those
based on the available radiant energy (Pg/La and Pn/La). Efficiencies
based on incident radiant energy include the capacity of the physical
system to transmit energy. The ability of the physical system of the
artificial streams to transmit energy can be represented by the ratio
La/Li and using the grand mean values of Table 8, this is 70.4%.

Calculations for the light intensity study revealed an increase in
energy transfer and a decrease in efficiency with an increase inrlight
intensity. Van Oorschot (1955) has reported lower efficiencies in algal
cultures when the light intensity was increased and Bonner (1962) has
theorized a decrease in efficiency with an increase in light when all other
conditions are optimum saying that this phenomenon is a function of light
intensity, quantum efficiency, and the light saturation level of the
chloroplasts. This phenomenon in the artificial streams may be a
function of light relationships as discussed by Bonner (_o_p. sit.) or it may
be due to a nutrient limitation on the upper level of energy fixation thus

causing the lower efficiency.

 

102

An energy flow diagram (Figure 19) was drawn to scale using
the grand mean values of Table 8. . It is readily apparent that a very
small amount of the incident energy is fixed as biomass. The energy

unavailable to the periphyton (Li - L islost in the water phase by

a)
reflection, scattering, and absorption. Some available energy is

also lost (La - Pg) by the algae at the bottom of the streams by reflection,
transmission, and processes of degradation. Further energy degrada-

tion by the algae is through respiration4(Pg -Pn).

Comparisons are made in Table 9 of the energy fixation rates,
as primary productivity, and the efficiencies of the artificial streams
with those of other ecosystems. When comparing productivity rates
the artificial streams are as low or lower than most of the natural eco-
systems. This is because the radiant energy of the artificial streams was
only about 1% of the average daylight intensity. Comparisons of efficiencies
reveal those of the artificial streams to be higherthan all natural
ecosystems except those for Silver Springs and other Florida springs for
which the values are similar. Efficiencies reported for algal cultures
are similar to those of the artificial streams. ‘Kok (1952) reported a
mean efficiency, presumed to be Pg/La, of 20% when all conditions were
optimum and the cultures were dense enough to use all of the available
light. -Kok's (_o_p. sit.) efficiency agrees exactly with .Bonner's (1962)
theory that the highest possible efficiency is 20%.

(One explanation of the high efficiencies obtained for the artificial
streams is based on the light quality of the ecosystem. The predominant
wavelengths of the incandescent lights are in the red range. Figure 20
illustrates a comparison of the daylight and incandescent spectra with
the absorbancy spectrum of the phytopigment extract. .It can be seen that
the relative amount of light received in the red range is much greater
from the incandescent bulbs than from daylight. The absorbancy of the

phytopigment extract is somewhat misleading when the large peak at

103

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enmsono escapes 034295 N 41H
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mend; Games 93 so @093 mamonum Hmfloflflmm 02$ E. Boa ewmposm, .2 ondwfim

104

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Amwoyg Sofiom Emofim _ Hope? 934.

105

Table 9. Comparisons of primary productivity and efficiencies for
various ecosystems.

 

 

 

 

Net Productivity Efficiencies (percent)
8 madav" £8 £8 E1 in
Ecosystem organic wt. g cal cm-‘Zday-1 (Li La ‘Li La
Arfificfifll 0.10 0.06 2L8 12.5 2.9 4.1
streams 0.46 0.20 2 l 3.0 0.9 1.2
Red Cedar River, 7’-
Michigan 0. 56 0. 07
Cedar Bog.Lake3 0.19 0.1 0.06
Minnesota Pond" 0 . 08 0. 02
Silver Spring55 7.4 2.42 5.3 0.52
Root springs6 1.79 0.27
Lake Mendota7 0' 27 0° 35
Algal culture8 1 to 13 l to 5
Florida Springs9 4. 0
Grand Coulee, 10
Washington . 05 to . 8

 

1Values are the maximum and minimum; ZGrzenda (1960); 3Lindeman (1942);
4Dineen (1953); 5Odum (1957a); 6Teal (1957); 7Juday (1940); 8Van Oorschot
(1955); 9Odum (1957b), and 10Castenholz (1960).

Li incident light energy, La 2 available light energy,
P

gross energy transfer, P = net energy transfer,

8

II

P - =
8/L1 Tropic level energy intake efficiency or Lindeman's (1942)
Pg/La- efficiency or photosynthetic efficiency

Pn/Li :
Pn/La

} Production efficiency

 

 

 

 

106

Figure 20. Comparison of the daylight and incandescent
spectra with the wavelengths absorbed by
phytopigment extracts.

Relative light distribution

 

Daylight spectrum

107

Inc andesc ent spectrum /

 

Absorbancy spectrum
for pigment

/
/
/

 

 

 

 

400

450

l l T '
500 550 600 650

Wavelength (mu)

Figure 20

700

Absorbancy percentiles

108

425 muis noted. According to Noddack andiEichhoff (1939) the maximum

absorbancy for-living cells of Chroococcus, a blue-green alga,.. is at

 

wavelengths of 683 mu (chlorophyll a) and 625 mu(phycocyanin). .Plant
physiologists and biochemists haveaccepted the theory that plants
absorb energy in terms of light quanta. It is also known that the energy
of a quantum of light decreases as the wavelength of the light increases.
A certain number of quanta, regardless of the wavelength, are required
to reduce a mole of carbon dioxide in photosynthesis. »Thus if the quanta
of light are of long wavelengths the efficiency is greater because less
energy is required. . Kok (1952) reported greater growth in Chlorella
cultures with monochromatic light of 650 mu than with flight at 440 mu.
Klugh (1930) also noted the greatest growth of algae under red light
when compared to green and blue light. The maximum photosynthetic
efficiency for a diatom was given at a wavelength of 655 mp. by Jenkin
(1937).

The high efficiencies are also partly explained by considering the
general increase in efficiencies when light intensities are decreased

(Van Oorschot, 1955, Bonner, 1962).

Nutrient Observations

Nutrient effects were not investigated as a particular phase of the
study, but inorganic and organic nitrogen and phosphorus were monitored
in an effort to keep the factors influencing productivity limited to the
characteristics under study. Water samples were collected weekly for
phosphorus and nitrogen analyses and the data for the overall study
were compared by streams. .If the nutrient levels of thetwo streams
are shown to be similar then further strength is given to conclusions
made from the studies of environmental characteristics. Nutrients

shown in Figure 7 indicate a general similarity between the two streams.

 

 

 

 

109

The nutrient concentrations for the two streams were also subjected to

a two-tailed matched pairs test. The statistical analyses showed that
the phosphorus concentrations of the two streams were not significantly
different at the 5% level (P = . 60), but the nitrogen concentrations were
different at the 1% level of significance (t = 3.618 > 0995 = 2.. 70, df = 43).

Although thematched pairs test indicated a difference in nitrogen,
the difference may not have been critical. The lower concentrations may
not have been limiting. Further interpretation of the nutrient concen-
trations was made after additional analyses of the data. The nitrogen
and phosphorus content of the organic weights of the algae were also
compared by streams. Since the samples were not taken simultaneously,
two-tailed "t” tests were used to compare the means of the organic nitro-
gen and phosphorus contents of the algae of the two streams. The
results of the ”t” tests indicated that the phosphorus content and nitrogen
content of the algae in stream 1 was not significantly different from
those of stream 2 at the 5% level (phosphorus: P = .60, nitrogen: P =
. 30). Apparently the difference in the available nitrogen of the two
streams did not greatly influence the organic composition of the algae.

(A comparison of the two streams in energy transfer rates in
Table 8 and nitrogen concentrations in Figure 7 reveals that high nitrogen
and high energy transfer coincide in the studies of temperature and light
intensity, but are opposite for the two streams in the studies of photo-
period and current velocity. It is assumed then that inorganic nitrogen
did not influence algal growth in one stream more than in the other
stream.

The biotic utilization of nutrients was investigated using a method
described by Grzenda (1960) for a study of the Red Cedar River. The
rates of phosphorus and nitrogen fixation were found to increase at
similar linear rates with the increase of growth rate (Figure 21). The

values for Figure 21 were based on analyses of periphyton collected on

110

Figure 21. Relationship between nitrogen and phosphorus
fixation by periphyton and periphyton growth.

Phosphorus Fixation (11g In'2 day'l)

1000

800

600

400

200

J

111

 

 

 

 

/ - 16
O—— Phosphorus /A
/
/
A—— Nitrogen /
/
/ e 14
/
A/
/
//
— 12
/
/
//
O/
/
/ A — 10
L 8
' 6
c 4
r 2
VLT ' l 1
100 200 300 400

Growth Rate (mg m_2 day'l)

Figure 21

Nitrogen Fixation (mg rn'2 day’l)

 

 

112

artificial substrates assuming the periphyton to be representative of
new growth on thestream bottoms. The rate of phosphorus fixation
by the blue-green algae in the artificial streams (about 2 pg .P Ing'w'l algae)
appears to be slightly less than the rate given by Grzendar(_o_p. git.) for
diatoms in theRed‘Cedar'River‘(about 3. 2 pg iP mg"1 algae), . at least in
the low growth rate ranges where the two studies are comparable.
The higher rate of fixation may be due to the much greaterconcentration
of phosphorus, about 6 fold, in the water of the RedCedar River or it
may be (due to a difference in the phosphorus requirements of the algal
communities. The rate of nitrogen fixation, although increasing at a
rate similar to phosphorus, is much greater per weight of periphyton
produced (Figure 21). This reflects the higher nitrogen requirement of
the periphyton. The rate of nitrogenfixation was roughly 43 pg N rng"1
algae.

The nitrogen and phosphorus content of the periphyton collected
on substrates was used to calculate the percent composition of the
organic weight (Table 10). Phosphorus calculations were based on the
analysis of 113 samples. The mean percent and standard deviation for
the phosphorus content of the organic weight was 0. 21 :1: 0. 11. The

conversion then from organic phosphorus to organic weight is

mg organic wt. = mg P x 476.

The capacity of algae to store phosphorus is well-known and is illustrated
here by the range of the percent of organic phosphorus from 0. 11 to

0.49. Gerloff andSkoog (1954) reported Microcystis aeruginosa to take

 

up phosphorus and nitrogen in proportion to the abundance of the nutrient
in the medium and gave organic phosphorus percentages of 0. 11 to 0.46.
There does not appear to be a relationship between the phosphorus con-
tent of the algae and the concentration of phosphorus in the media in

Table 10. The lowest phosphorus concentrations (light intensity study)

113

Table 10. The phosphorus and nitrogen composition and N/P quOtients
for the organic 'weight of periphytonfrom the artificial. streams.

 

 

 

 

Mean nutrient conc. 'Organic composition
Stream ‘P N N/P
Study "Number (Hg‘liter'l) (mg'liter'l) ‘P(%) N(%) quotient
Tempera- >:<
ture 1 20.5 1.90 0.12 -- --
2 23.5 3.68 0.11 1.38 12.5
Photo—
period 1 16.4 0.93 0.16 5.17 32.3
2 16.2 1.26 0.14 3.72 26.6
Light
Intensity 1 4.8 0.18 0.26 2.95 11.3
2 4.0 0.25 0.18 2.28 12.7
Current
Velocity 1 13.3 0.28 0.22 4.00 18.2
2 13.6 0.41 0.23 4.17 18.1
Chelate 1 12.8 0.21 0.49 5.36 10.9
2 10.0 0.21 0.43 3.94 9.2

 

' Samples contaminated.

gave intermediate organic phosphorus percentages indicating that
phosphorus was not limiting.

The nitrogen content of the periphyton was estimated from the analy-
sis of 62 samples giving a mean percent and standard deviation of 3. 29 :1:

1. 63. The conversion from organic nitrogen to organic weight is

mg organic wt. = mg N x 30.4.

114

The Anitrogencontent of algae is also quite variable as shown by the range
in Table 10 of 1. 38% to 5. 36%. Gerloff andSkoog (1954) reported a
range of nitrogen percent of 3. 16 to 7.72%, .Spoehr andMilner‘(l949)
reported a range 'of 1. 17 to 14. 11%, and Ketchum and'Redfield-(l949),
a range of 2.. 6 to 8. 6%. .As with the phosphorus data, one of the highest
nitrogen concentrations during the studies is paired with the lowest
nitrogen content (Table 10) also indicating that nitrogen was probably not
a limiting factor.

The ratio of the nitrogen content to the phosphorus content is the
N/P quotient and was calculated as 15. 9 for the overta’ll study. -N/P
quotients for the individual studies are given in Table 10. Comparison
of the N/P quotients with rates of energy tranfer in Table 8 reveal little
relationship; however, the high N/P quotients for the photoperiod study
are due to the addition of NH4NO3 to the media during that study.
The readily available ammonium ion probably caused the high organic
nitrogen content. When the ‘N/P quotients of the photoperiod study are
disregarded, high N/P quotients appear to be related to high productivities.
This is reasonable if one considers rapid growth rates to be accompanied
by low phosphorus storage in the algal cells or a high rate of protein
synthesis or both.

-Since the main supply of nutrients depended upon decomposition of
organic matter in the reservoirs and filter boxes, a brief study was
undertaken to determine the rate of phosphorus regeneration. Masses
of senescent algae were drained and placed in flasks of distilled water
or stream water and stored in the dark for a number of days. The ortho-
phosphate concentration of the water was determined upon removal of
the flasks from dark storage. The results in Table 11 indicate that the
blue-green algae were easily decomposed. The higher rate of phos-
phorus regeneration occurring in the flasks with stream water may

indicate that decomposition was largely by bacteria rather than by

115

Table 11. Phosphorus regeneration from decomposition of algae placed in
100 ml water and stored in the dark at 25 C.

 

 

Algae in grams Incubation Released Rate of P2
Water type wet weight in days P1 in 1.1g released
Distilled 13.433 5.9 44 0.55
Distilled 14.401 7.0 400 4.00
Stream 16.310 2.0 260 8.00
Stream 13, 517 11.7 1400 8.85

 

1Released phosphorus as orthophosphate.

2Rate in micrograms P per gram of wet algae per day.

autolysis. The rate of phosphorus regeneration occurring in the flask
of distilled water incubated for 7. 0 days was much higher than in the
flask of distilled water incubated for 5. 9 days and can be explained by
allowing a time period for a bacterial population to build up, since some
bacteria must have been present in the stream water adhering to the
algae prior to placement of the algae into the flasks. Golterman (1960)
studied cycling of elements and reported that 70 to 80% of the organic
phosphorus leaves freshly killed algal cells by autolysis in a few days
under sterile conditions. Golterman also noted that only the phospho-
proteins required breakdown by bacteria. It is difficult to explain the
results in Table 11 on the basis of autolysis since the algae were not
killed prior to placement in the flasks. .If the regeneration did not occur
by bacteria or autolysis, it might be explained by metabolic release of
phosphorus across cell walls occurring when the algae utilized stored
food in the extended period of respiration. This explanation does not

account for the difference between distilled and stream water.

116

Regardless of the explanation it can be assumed that phosphorus
regeneration occurred in the dark areas of the artificial streams at
a daily rate of approximately 8 ug P g"1 algae.

Another brief nutrient study was undertaken to determine the
practicality of removing phosphorus from the medium using suspension
of kaolin. Suspensions of kaolin were added to each-stream until the

'1. ‘One of the streams was

concentration approached 100 mg liter
acidified with acetic acid prior to the kaolin addition. The results in
Table 12 show that phosphorus was removed from the acidified stream,
but not from the unmodified stream. After a period of 3 hours a concen-
tration of 21 ug P liter“1 or a total of 5166 pg P had been removed from
solution in the acid stream. This is a removal ratio of 21:100, 11g szg
kaolin. The amount of phosphorus removed is small compared to the
amount of kaolin added; however, the exposure time was short and the
kaolin precipitated rapidly on the stream bottom. If an agitation

system were employed the removal efficiency may be increased.

The exact relationship underlying the fixation of phosphorus by
kaolinite is not known. Black (1942) has shown that kaolinite has a high
affinity for soil phosphorus at pH 4. 5 and that this affinity decreases
to a low at pH 7. 9. 1 Black also demonstrated that a 30 day contact period
fixed a much greater amount of phosphorus than a48-hour period. This
indicates that a longer contact period than allowed in the stream studies
is necessary for efficient removal of phosphorus. Theories for the

action of kaolinite fixation of phosphorus have been given by Black (22. C_it)

and Hemwell (1957).
Concluding Remarks

The general agreement of results of the environmental studies
with theoretical expectations and with similar studies in natural and

other laboratory systems indicates several things. The methods used

117

Table 12. Removal of phosphorus. from solution by the addition of 100 mg
liter-l kaolin to each artificial stream.

 

Soluble phosphorus

 

Sampling Stream Total alkalinity concentration in
time “Number pH (mg liter"1 caco3) stream water (11g liter’l)
Pre-
kaolin 1 5 . 70 60 74
2 8. 50 103 130

0. 5 hr. after
kaolin 1 5 . 84 60 61

2 8.53 98 124
3 hrs. after
kaolin 1 5.86 60 53
2 8.78 99 133

 

to measure productivity in flowing water, i. e. , pH-carbon dioxide changes,
oxygen changes, and periphyton collected on artificial substrates, are
sufficiently sensitive to reflect the effects of factors influencing the rate

of production. »Artificial streams, as used in this study with adequate
areas for decomposition and recycling of nutrients and with sufficient

time allowed for the systems to become established, are reasonable
replicas of natural systems allowing extension and application of the re-
sults to streams in general. The magnitudes of the productivities and
efficiencies estimated for the artificial streams are also in agreement

with those of natural systems indicating that the carbon dioxide and

oxygen methods are reasonably accurate as well as sensitive.

 

 

SUMMARY

1.. Primary productivity in two, artificia,l,, recirculating streams
was measured by the pH-carbon dioxide method, the upstream-down-
stream oxygen method, and by collection of periphyton on artificial
substrates.

2.. Productivity increased significantly when the environmental
characteristics of light intensity, current velocity, and chelate were
individually increased.

3. An increase in temperature caused a net productivity increase
significant at the 10% level and at Q10 value of 1.4 indicating that
respiration increased at about the same rate as photosynthesis. The
effects of altered photoperiod on net productivity were not significant.

4. . Productivity measured by the ash-free dry weight of periphyton
collected on artificial substrates was generally lower than estimates
by the carbon dioxide and oxygen methods; however, the substrate
estimates increased when they were based on the growth rate occurring
on the last few days of an extended exposure period. The growth of
the periphyton population was described as having a J- shaped form.

5.. Estimates of net productivity by the carbon dioxide method
and the oxygen method were in general agreement when the oxygen values
were corrected by a photosynthetic quotient in the range of 1.1 to 1. 3
depending upon the measured caloric values of the periphyton.

6. The relationship between ethanol phytopigment extractions and
ash-free dry weights of the periphyton was linear. .A common regression
equation, indicated by statistical analysis, was calculated with the
relationship having a correlation coefficient of . 946. The possibility of a
consistent phytopigment-organic weight relationship based on community
homeostasis is discussed.

118

 

119

7. The flow of energy through the ecosystem was traced from a
source of radiant energy. from incandescent bulbs to fixation as the
chemical energy of organic matter. The periphyton of the artificial
streams fixed energy in a range of 0. 06 to 0. 20 g cal cm‘z day"1 being
somewhat less than the rates of most natural communities. - However,
the light received by the artificial streams was much less than that of
natural communities, being about 1% of the average daylight intensity.
Thus efficiencies of productivity were relatively high for the artificial
streams and are explained on the basis of light quality and intensity.

8. The efficiency of energy transfer increased when productivity
increased in most cases. An increase in productivity caused by a
higher light intensity was accompanied by a decrease in the efficiency.

9.. Phosphorus concentrations were shown to be similar in the
two-streams while nitrogen concentrations were different. The effects
of the different nitrogen concentrations were negligible as shown by
lack of effects on the algal composition and on productivity. 1 The rate of
phosphorus and nitrogen utilization increased as productivity increased.

10. The rate of phosphorus regeneration by decomposition of
algae was estimated and shown to occur readily in the dark areas of
the streams. Phosphorus release from insoluble sources occurred
with the addition of a chelate while suspensions of kaolin were used to

precipitate phosphorus under acid conditions.

 

 

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