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dissertation entitled

Fish Production, Primary Productivity and
Nutrient Availability in Fertilized
Fish Ponds in Malaysia

presented by
Fat imah Md .Yusoff

has been accepted towards fulfillment
of the requirements for

Fisheries & Wildlife

 

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M ajorikofessor

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FISH PRODUCTION, PRIMARY PRODUCTIVITY AND NUTRIENT AVAILABILITY IN
FERTILIZED FISH PONDS IN MALAYSIA

3!"

Fatimah Md.Yusoff

A DISSERTATION

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

DOCTOR OF PHILOSOPHY

Department of Fisheries and Wildlife

1987

53055ef

ABSTRACT

FISH PRODUCTION, PRIMARY PRODUCTIVITY’AND NUTRIENT AVAILABILITY IN
FERTILIZED FISH PONDS IN HAMYSIA

By

Fatimah Hd.Yusoff

Four fish species, A:1151§h§h31_ngh1111_(Richardson),
WWW” Munich. :11de
(Bleeker) were grown for 352 days in three treatments: a reference
treatment, triple super phosphate (TSP) treatment and triple super.
phosphate plus urea (TSP-urea) treatment. Reference ponds received no
fertilizer, while TSP ponds received 28.3 kg P205/ha/mcn, and TSP-urea
ponds received 7.1 kg P205/ha/wk plus 35.5 kg urea/ha/wk. Net fish
productions were 437 kg/ha, 1034 kg/ha and 1713 kg/ha in reference, TSP
and TSP-urea treatments respectively.

Mean gross primary productivity was 0.09, 0.17 and 0.26 g C/mZ/hr
and mean net productivity was 0.08, 0.12 and 0.21 g C/mz/hr for
reference, TSP and TSP-urea treatments respectively. Reference, TSP and
TSP-urea treatments had daily changes of total inorganic.carbon of 1.04,
1.48 and 2.41 g C/mz/day. Chlorophyll a concentrations were 12.50
mg/m3, 46.71 mg/m3 and 109.18 mg/m3 in reference, TSP and TSP-urea

treatments respectively. Differences between treatments for fish

production. algal production and chlorophyll g were significant (p <
0.05) except for net production in reference and TSP treatments. let
fish production‘waa positively correlated to gross and net primary
productivity. and chlorophyll g.

Viekly analyses of orthophosphate-P revealed that mean
concentrations were highest in the TSP treatment (0.033 mg/l.) followed
by the TSP-urea treatment (0.009 mg/L) and.the reference treatment
(0.003 mg/L). An.inorganic nitrogen to orthophosphate-P ratio of 36 in
reference ponds indicated a phosphorus shortage. A ratio of 2 in TSP
ponds indicated nitrogen shortage. A ratio of 44 in TSP-urea ponds
suggested phosphorus was in.short supply. '

Bioassay tests using the alga figlgnggsxul ggpxiggxnggu.
Printz,supported the above contention.by showing higher growth in
response to phosphorus enrichment of reference pond water relative to
control cultures, response to nitrogen addition in TSP treatment water
and response to phosphorus addition in TSP-urea treatment water. Input
of phosphorus and nitrogen fertilizers to provide well balanced
concentrations for algae uptake was important to increase and maintain

high primary productivity and thus fish yield in these fish ponds.

To Hy Family

iv

ACKNOWLEDGMENTS

I would like to express my most sincere gratitude and thanks to my
major professor, Dr. Clarence D. McNabb whose unceasing encouragement,
guidance and inspiration propelled me to undertake this difficult task.
His willingness to come to Malaysia to discuss and advise on my research
is deeply appreciated. I also wish to thank Dr. Donald L. Carling, Dr.
Donald J. Hall, Dr. Peter C. Murphy, and Dr. Gary Marx for their
invaluable guidance and advise throughout my program as they served on
my graduate committee.

My heartfelt thanks go to Dr. Ted R. Batterson for his invaluable
and generous help during the preparation of this dissertation. Thanks
are also extended to my colleagues, Dr. A.K.M. Mohsin, Dr. Azmi Ambak
and En. Aizam Zainal Abidin from the Faculty of Fisheries and Marine
Science, Universiti Pertanian Malaysia, for their continual support
during all phases of my research.

My deepest appreciation goes to my husband, Dzulkafli, whose
perpetual encouragement and support made this task feasible, and to my
children, Irman Hadi and Suriani who had to bear with my long absence
during the completion of this work.

This program was sponsored by the Government of Malaysia (Public

Services Department, Malaysia) and the Universiti Pertanian Malaysia.

LIST OF TABLES

LIST OF FIGURES .

INTRODUCTION

MATERIALS AND METHODS .

RESULTS .

DISCUSSION

LITERATURE CITED

APPENDIX

TABLE OF CONTENTS

vi

Page
viii

ix

21
47
59

66

LIST OF TABLES

Table Page

1. Amount of fertilizers applied to experimental fish ponds
during 1986 and 1987. TSP is triple super phosphate . . . . ll

2. Total monthly rainfall and evaporation, mean daily relative
humidity, wind speed, and mean daily maximum and minimum air
temperature . . . . . . . . . . . . . . . . . . . . . . . . 22

3. Limnological characteristics of pond water in experimental
ponds during 1986 and 1987. Values are means i one standard
error. Number of samples is given in parentheses. Ranges
are given in brackets for pH. TSP is triple super
phosphate . . . . . . . . . . . . . . . . . . . . . . . . . 23

. 4. The growth characteristics of fish in experimental polycul-
ture ponds during 352 day grow-out period. TSP is triple
super phosphate. . . . . . . . . . . . . . . 26

5. Mean primary productivity, mean chlorophyll 5 concentrations
and net fish production in 3 treatments during 352 day grow-
out period. Values are means i one standard error. Number
of samples is given in parentheses. TSP is triple super
phosphate.. . . . . . . . . . . . . . . . . . . . . . . . . 29

6. Mean concentrations of nutrients i one standard error in
experimental fish ponds under different treatments. Number
of samples is given in parentheses. TSP is triple super

phosphate.. . . . . . . . . . . . . . . . . . . . . . . . . 36

7. Mean nutrient concentrations and ratios in bioassay water
from reference, TSP and TSP-urea treatment ponds on March 17,
1987. TSP is triple super phosphate. ... . . . . . . . . . 41

8. Mean nutrient concentrations and ratios in bioassay water
from reference, TSP and TSP- -urea treatment ponds on March 24,
1987. TSP is triple super phosphate. . . . . . . . . . . . .42

9. Mean nutrient concentrations and ratios in bioassay water

from reference, TSP and TSP-urea treatment ponds on March 31,
1987. TSP is triple super phosphate. . . . . . . . . . . . .43

vii

10.

Mean concentrations of phosphorus and nitrogen (mg/L) pre-
sent and required for the observed carbon fixation in ex-
perimental fish ponds in Malaysia during 1986 and 1987.
TIN is total inorganic nitrogen. TSP is triple super
phosphate.. . . . . . . . . . . . . . . . . .

viii

. 51

Figure

LIST OF FIGURES

Page

Net fish production for A. 2221112, Q. 122112, E. 3221222;
222 and 9. 221212 during 352 day grow-out period in reference,
TSP and TSP-urea treatment ponds. TSP is triple super
phosphate. . . . . . . . . . . . . . . . . . . . . . . . . 27

Mean concentrations and fluctuations of chlorophyll 2

in reference, TSP and TSP- -urea treatment ponds during 1986 and
1987. TSP is triple super phosphate. Broken lines indicate
lapse in sampling time. . . . . . . . . . . . . . 30

Linear regression analysis of net fish production and gross
primary productivity in experimental ponds during 1986 and
1987. R is reference, T is TSP treatment and TU is TSP-urea
treatment. TSP is triple super phosphate. . . . . . . . . 32

Linear regression analysis of net fish production and net
primary productivity in experimental ponds during 1986 and
1987. R is reference, T is TSP treatment and TU is TSP-urea
treatment. TSP is triple super phosphate. . . . . . . . . 33

Linear regression analysis of net fish production and daily
change in total inorganic carbon in experimental ponds

during 1986 and 1987. R is reference, T is TSP treatment and
TU is TSP-urea treatment. TSP is triple super phosphate. . 34

Linear regression analysis of net fish production and chloro-
phyll 2 concentrations in experimental ponds during 1986 and
1987. R is reference, T is TSP treatment and TU is TSP-urea
treatment. TSP is triple super phosphate. . . . . . . . . 35

Effects of various nutrient additions on the growth of S.
2221122122222 in water from.reference, TSP and TSP-urea treat-
ment ponds on March 17, 1987. PW is pond water, P is phos-
phorus, N is nitrogen, C is carbon, Bold's is Bold's basal
medium, and TSP is triple super phosphate.

38
Effects of various nutrient additions on the growth of S.
2221122Ingggn in water from reference, TSP and TSP-urea treat-
ment ponds on March 24, 1987. PW is pond water, P is

ix

10.

A-l.

A-2.

phosphorus, N is nitrogen, C is carbon, Bold's is Bold’s
basal medium, and TSP is triple super phosphate.. . . . . . 39

Effects of various nutrient additions on the growth of 5.
2221122122222 in water from reference, TSP and TSP ourea
treatment ponds on March 31,1987. PW is pond water, P is
phosphorus, N is nitrogen, C is carbon, Bold's is Bold's
basal medium, and TSP is triple super phosphate.. . . . . . 40

Mean free carbon dioxide over daylight hours in reference,

TSP and TSP-urea treatment ponds during 1986 and 1987 in
relation to air-water equilibrium concentrations of carbon
dioxide. TSP is triple super phosphate. . . . . . . . . . 56

Mean concentrations of orthophosphate- -P in reference,TSP and
TSP- ~urea treatment ponds during 1986 and 1987. TSP is triple
super phosphate. . . . . . . . . . . . . . . . . 66

Mean concentrations of total phosphorus in reference, TSP
and TSP-urea treatment ponds during 1986 and 1987. TSP is
triple super phosphate.. . . . . . . . . . . . . . . . . . 67

. Mean concentrations of nitrate+nitrite nitrogen in reference,

TSP and TSP-urea treatment ponds during 1986 and 1987. TSP
is triple super phosphate. . . . . . . . . . . . . . . . . 68

. Mean concentrations of total ammonia nitrogen in reference,

TSP and TSP- -urea treatment ponds during 1986 and 1987. TSP
is triple super phosphate. . . . . . . . . . . . . . 69

INTRODUCTION

The main objective in most aquaculture research programs in less
developed countries is to increase fish production beyond that obtained
with practices in use. Increasing fish production by feeding fish is
less appealing and less economical in these countries where food for
human consumption is often in short supply. Therefore, promoting growth
of natural foods such as plankton and benthos, is a preferred means of
increasing fish productivity in these areas.

Many investigations have shown positive correlations between pond
fertilization and fish production. Swingle and Smith (1938) reported
that addition of inorganic fertilizer greatly increased fish production
in ponds. Later, Swingle (1947) found that fertilization always
resulted in appreciable increase in standing crop of bluegills and
largemouth bass. Addition of inorganic fertilizers to fish ponds
increased yields of sunfish from 3 to 4 times the yields from
unfertilized ponds (Boyd 1982). Schroeder (1974) similarly reported
that harvest of carp and tilapia increased 25% to 100% in ponds
fertilized with fluid cowshed manure.

The increase in fish productivity in fertilized ponds has been
attributed to an increase in primary production (Melack 1976; Almazan
and Boyd 1978). Increases in phytoplankton productivity with

application of both organic and inorganic fertilizers has been

2
demonstrated by many workers (e.g. Langford 1948; Ball 1949; McIntire
and Boyd 1962; Dendy et a1. 1968). Fertilization also results in an
increase of chlorophyll 2 many times over those ponds without
fertilization (Brook 1958; Hepher 1962 a; Hall et a1. 1970; Schindler
1971; Boyd 1973, 1976). Phytoplankton growth in turn increases '
zooplankton production, thereby favoring greater yields of fish
(Stickney 1979; Seymour 1980). During a study at the State of Michigan
hatcheries, Ball (1949) found that populations of planktonic organisms
and bottom invertebrates had considerably higher biomass in fertilized
compared to unfertilized ponds.

Factors such as light, temperature and nutrients play an important
role in determining phytoplanktonic productivity in aquatic systems
(Hutchinson 1967; Telling 1971; Wetzel 1983). Due to warm climate and
shallowness of most tropical fish ponds (1.0 m to 1.5 m), temperature
and light (McNabb, et al. 1988) are not likely to be limiting. Instead,
nutrients may play a major role in controlling phytoplanktonic
productivity in aquaculture ponds since they are usually in short supply
due to extremely leached soil in the wet tropics (Yaacob and Shamsuddin
1982).

An important aspect of successful aquaculture management in
extensive culture systems; that is those with endogenous food sources
only, is a constant supply of basic nutrients in the form of phosphorus,
nitrogen and-carbon compounds. Phosphorus has been implicated as the
key nutrient because natural concentrations of phosphorus in pond waters
are thought to be too low to support abundant phytoplankton populations

(e.g. Sawyer 1952; Wahby 1974; Boyd and Musig 1981).

3

Orthophosphate present in water immediately after fertilization may
be taken up by phytoplankton, bacteria, or sediments (Rigler 1956, 1964;
Hayes and Phillips 1958; Hepher 1958; Fitzgerald 1970; Kimmel and Lind
1970). Because of this, concentrations of soluble orthophosphate
present after fertilizer application usually decline by 90% within 1 to
2 weeks (Zeller 1952; Hepher 1958, 1963; Boyd 1981). However, due to
the accumulation of phosphorus in the sediment over time, the mud in
fertilized ponds has a gradually decreasing ability to remove phosphorus
from water (Eren et a1. 1977). This results in greater availability of
fertilizer phosphorus to phytoplankton in older ponds.

Phytoplankton productivity in fertilized ponds usually varies from
moderate to high when fertilizers are applied at widely spaced intervals
(Dobbins and Boyd 1976). Hepher (1963) found that fish yields were
lower in ponds where inorganic fertilizer was applied twice at the
beginning of the growing season than in ponds where fertilizer was
applied every two weeks. Hepher (1958) and Boyd and Musig (1981)
suggested that high rates'of primary production, necessary for intensive
fish production, depend upon frequent application of phosphate
fertilizer to keep orthophosphate above the concentration required for
equilibrium at mudawater interphase. Thus, the frequency of fertilizer'
application was important in determining pond productivity.

In spite of popular belief that phosphorus is the most important
element in pond fertilization, there appears to be some disagreement
over the correct fertilization procedures to use in aquaculture. In
Europe, it is believed that treating ponds with phosphorus alone

increases nitrogen fixation to such an extent that additional nitrogen

4

is unnecessary (Hickling 1962). Lahnovitch (in Seymour 1980) listed
three types of fertilization practice; non-nitrogenous fertilization
used in Germany, mixed N-P-K fertilization used in the U.S.A., and
nitrogen and phosphorus fertilization used in the Soviet Uhion.
However, idea that only phosphorus is necessary in fish ponds has become
established in many parts of the world from the European experience.

This view was supported by Swingle et a1. (1963) who demonstrated
that nitrogen plus phosphorus fertilization was generally no more
effective than phosphorus fertilization alone in increasing yields of
carp, goldfish and channel catfish in old fish ponds in Alabama which
had received earlier applications of N-P-K fertilizers. They concluded
that sufficient nitrogen came from mineralization of organic matter in
bottom muds, and from nitrogen fixing bacteria and blue-green algae.
Fish ponds in Alabama have high percentages of blue-green algae, many of
which are nitrogen fixers (Boyd 1973). Rappaport et a1. (1977) observed
90% blue-green algae and 10% diatoms and green algae during their
organic fertilization experiment. Boyd and Sowles (1978), also working
in Alabama found that nitrogen and phosphorus fertilization of sunfish
ponds did not increase fish production above that achieved with
phosphorus fertilization alone. Hickling (1962) and Boyd (1979)
maintained that nitrogen is often not essential in pond fertilizers
because nitrogen fertilization fails to appreciably increase inorganic
nitrogen concentration, phytoplankton biomass and fish yields. Other
investigators argue that nitrogen fertilizers are unnecessary because

either phosphorus increases blue-green algae which are capable of fixing

5
nitrogen (Seymour 1980), or denitrifying bacteria breakdown the added
nitrogen to nullify its effect (Wahby 1974).

The use of phosphorus fertilizer without nitrogen appears to
promote development of blue-green algae by causing high algae biomass,
the growth of which becomes limited by carbon dioxide or nitrogen. King
(1970) and Shapiro (1973) suggest that blue-green algal dominance may
increase with decreased carbon dioxide concentration since blue-green
algae are competitively better at lower carbon dioxide levels than green
algae. Seymour (1980) demonstrated that heterocyst-forming blue-green
algae are favored in competition with other species in waters with a
relatively low nitrogen content. Smith (1983) reported that lack of
nitrogen leads to dominance of blue-green algae in lake phytoplankton.
Species of the blue-green alga 52222222 and other nitrogen fixers also
have competitive advantage over non-nitrogen fixing algae with respect
to growth, since growth and buoyancy of the former are increased under
nitrogen limiting conditions (Walsby and Klemer 1974; Van Rijn and Shilo
1983, Spencer and King 1983).

Excessive growth of blue-green algae may cause severe dissolved
oxygen depletion in fish ponds (Swingle 1968). Dobbins and Boyd (1976)
and Boyd et a1.(198l), had blooms of 52222222,2211221112 in their
phosphorus and potassium fertilization experiments, and dissolved oxygen
declined to 0.5 mg/L following decay of dead algae. In addition, some
blue-green algae excrete geosmin, a compound with an earthy-musty flavor
and odor, giving an off-flavor taste to flesh of cultured fish (Aschner
et a1. 1967; Lovell and Sackey 1973; Richards 1978), whilst others are

thought to release toxins causing fish mortalities (Shilo 1957; Gorham

6
1964; Sawyer et a1. 1968: Gentile and Maloney 1969). Some species of
blue-greens possess buoyant gas vacuoles and accumulate at the pond
surface during warm, calm weather, and limit light penetration into the
pond, thereby depressing the productivity per unit area of the pond.

Hence, blue-green algae can be undesirable and deleterious in fish
farming. Many workers report that blue-green algae can be kept at bay
by manipulating the ratio of total nitrogen to total phosphorus
(Schindler 1977; Flett et a1. 1980; Smith 1983). Other studies report
absence or non-dominance of blue-green algae in waters with high
nitrogen concentrations (Ewing and Dorris 1970; Hall et a1. 1970; Green
et a1. 1976).

Besides controlling blue-green algae dominance, there is evidence
to suggest that nitrogen is important in regulating primary productivity
and algal biomass in pond waters. Sakamoto (1966) reported that
chlorophyll yield was a logarithmic function of both total nitrogen and
total phosphorus. Moss (1969) indicated that nitrate and nitrate plus
phosphorus were potentially limiting to algal growth in some Central
African waters. Zaret et a1. (1981) demonstrated a significant effect
of nitrogen in increasing chlorophyll production in Lego Jacaretinga,
Brazil. Other workers report that nitrogen and phosphorus were limiting
to algal productivity at different times of the year (White and Payne
1977; Setaro and Melack 1984). In this light, more attention needs to
be focused on nitrogen as an important element in aquaculture
fertilization practice.

In Malaysia, aquaculture is a relatively new industry introduced by

the Chinese immigrants about 40 years ago. To date, the culture of

7
freshwater fish using traditional methods has dominated aquaculture
activities in Malaysia. Aquaculture research and training in this
country are very much in their infancy. Modifications of traditional
culture practice have usually followed recommendations made from other
countries, such as the United States of America, EurOpe, Israel and
Japan where aquaculture research has been more intensive. At present,
the routine practice in pond culture in Malaysia includes lining the
pond bottom at a standard rate of 1,000 - 1,500 kg/ha of calcium oxide
and fertilization with inorganic fertilizer at the rate of 400 kg/ha/yr
of double super phosphate or 340 kg/ha/yr of triple super phosphate. If
organic fertilizer is used, it is applied at the rate of 7,500 - 10,000
kg/ha/yr (Malaysian Fisheries Deparment 1985).

In recent years inorganic fertilizers have been more frequently
used as they are readily available in Malaysia. In fact, inorganic
fertilizers have been shown to be more effective than manure in
increasing fish yields. The Tropical Fish Culture Research Institute
(1959-1960) reported that 18 kg P205 produced higher fish yield than
6.75 tons of cowdung. The Institute felt that not only were phosphate
and urea far more efficient in fish production than cowdung, but they
were considerably cheaper. Furthermore, problems associated with
organic fertilization, such as serious oxygen depletion, foul odor,
diseases and hygiene raise the question whether traditional organic
fertilization is more economical and appealing than inorganic
fertilization.

. Based on Malaysian Fisheries Department recommendations, Malaysian

fish farmers do not apply nitrogen fertilizer to their ponds.

8
Phosphorus fertilization which is recommended at monthly intervals, has
the potential to promote nitrogen shortages in ponds. Shortages in
nitrogen could result in lower primary productivity and fish yield.
Monthly application of phosphorus fertilizer could also lead to
shortages in phosphorus as if it is lost to sediments and outflow.

The purpose of this study was to test the effects of nitrogen
fertilizer in combination with phosphorus on primary productivity, algal
biomass and fish production. Theoretically, addition of phosphorus
fertilizer alone could increase carbon fixation until the nitrogen
supply became exhausted. At this point, addition of nitrogen fertilizer
could relieve nitrogen shortage and further increase primary
productivity until some other growth factor became limiting. To test
the above predictions, 3 treatments were used: reference, phosphorus
fertilizer and phosphorus plus nitrogen fertilizers. Phosphorus
fertilizer was applied monthly, and phosphorus plus nitrogen fertilizers
weekly to illustrate productivity obtained with short interval
fertilizer application. To verify nutrient shortages in ponds of
different treatments, nutrient bioassay experiments were performed. The
goal was to identify the most effective fertilizer procedure to obtain

high primary productivity, algal biomass and fish production.

MATERIALS AND METHODS

POND PREPARATION

Nine ponds located at the Agriculture University of Malaysia, were
used in this experiment. Weather data was obtained from the Department
of Soil Science, Agriculture University of Malaysia. Each pond measured
12 m‘by 27 m giving a surface area of 324 m2. ‘For the purpose of this
experiment, standard pond preparation and culture practices recommended
by the Malaysian Department of Fisheries (1985) were used. All ponds
were completely drained and left to air-dry for 7 days. Since the pH of
water prior to liming was less than 6.50, 6 ponds were lined with
quicklime (calcium oxide) at a rate of 634 kg/ha (20.5 kg/pond) on March
28, 1986. Quicklime is usually used by fish farmers instead of
limestone due to the fact that quicklime has a faster reaction in
raising pH of pond water. In addition, it kills wild fish and parasites
in ponds. The other 3 ponds served as references and were not subjected
to liming.

On April 18, 1986, water from a nearby reservoir was used to fill
all the ponds to l m depths. Saran nets covered inlets to prevent wild
fish from entering the ponds. ’Pond depths were controlled with monk
outlets (Huet 1975). Water levels were maintained by periodic additions

of water through inlet pipes. Clay was packed between the two sets of

10
wooden planks in monks to prevent leakage. Planks are taken out when
emptying the ponds.

On May 9, 1986, an inorganic fertilizer, triple super phosphate
(TSP: 0-46-0), was broadcast at a rate of 28.3 kg/ha on 6 limed ponds.
Fish fingerlings were stocked on May 20, 1986 in all ponds. Fish
species and stocking rates used followed those recommended by the
Malaysian Fisheries Department (1985):

Aristichthxs_nchilis (Richardson) (big head carp) at 12
fish/pond with mean weight of 6.9 g,

Qtsnsnhsxxnssdsn_idslla Val. (grass carp) at 8 fish/Pond with
mean weight of 4.8 g, I

Qyp;1222_22;212 L. (common carp) at 40 fish/pond with mean

weight of 0.5 g, and

£22212§_g2212n2222 (Bleeker) (Indonesian carp) at 100

fish/pond with mean weight of 0.2 g.

The overall rate of stocking was 0.5 fish/m2.

Six weeks following initial triple super phosphate application,
three of the six treatment ponds were fertilized on a weekly basis with
triple super phosphate and urea (46-0-0). The amount of TSP added
weekly was one-fourth the amount used monthly in the remaining three
treatment ponds. The amount of urea added weekly was five times the
amount of TSP added weekly. Table 1 summarizes treatments used in the
experiment. The experiment was terminated with the harvest of fish 352

days after they were stocked.

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12
SAMPLING AND ANALYSES

Temperature, dissolved oxygen, pH and alkalinity were measured
weekly at approximately 4 hour intervals from dawn till dusk from May to
July 1986, and in April 1987. Oxygen and temperature were measured in
the center of each pond at 0.25 m depth intervals using a YSI model 57
dissolved oxygen meter with temperature indicator. Water samples for pH
and alkalinity were collected from the center of each pond by pooling 2
samples from 0.25 m and 0.75 m depths using Van Dorn water sampler. The
pH was determined using a pH meter, with combination electrode, model
Metrohms Herisau E 603. Alkalinity was measured by titrating 100 mL
samples with 0.01N HCl using mixed bromcresol green-methyl red indicator
(wetzel and Likens 1979). Free carbon dioxide, bicarbonate, carbonate
and total inorganic carbon.were calculated from pH, alkalinity and
temperature data using a spreadsheet program (see wetzel and Likens
1979). Specific conductivity was determined weekly using a YSI
salinity-conductivity-temperature meter. Underwater light was measured
at 0.25 m depth intervals using a quantum meter (LICOR LI-888).

Water samples for chemical analyses were collected weekly from May
to July 1986, and in February to April 1987 from the center of each pond
by pooling 2 samples from 0.25 m below water surface and 0.25 m above
the bottom layer using Van Dorn water sampler.

For soluble reactive phosphorus analysis, 50 mL of the filtered
samples (using pore size 0.45 micron membrane filters) were adjusted to
pH 6-8 with 5N H2804 and 1N NaOH. Eight milliliter of combined reagent
(5N H2804, antimony potassium tartrate, ammonium molybdate and ascorbic

acid) were added to all samples and standards. Absorbance was measured

13
after 10 minutes at 880 nm using a double beam spectrophotometer
(Shimadzu UV-210 A). ‘Results of soluble reactive phosphorus
determinations are reported in this paper as orthophosphate-P. For
total phosphorus analysis, samples and standards of 50 mL each were
digested by adding 1 mL llN H2804 and 0.4 g ammonium persulphate and
evaporated on hot plate until a volume of 10 mL was reached. Samples
and standards were then adjusted to pH 6 to 8 with NaOH and diluted to
50 mL with deionized water before being subjected to the same procedure
as for dissolved reactive phosphorus (American Public Health Association
1985).

Samples and standards of 10 mL each were used for ammonia-nitrogen
measurements. The following reagents were added to each: 0.05 mL of
MnSOh, 0.5 mL of hypochlorous acid reagent and 0.6 mL of phenate
reagent. After 10 minutes absorbance was measured at 630 nm using a
double beam spectrophotometer (Wetzel and Likens 1979).

For nitrate+nitrite nitrogen analyses, all samples were filtered
through 0.45 micron membrane Millipore filters. To 25 mL of each
filtered sample and standard, 75 mL of ammonium chloride-EDTA solution
were added. Samples and standards were then passed through an activated
cadmium reduction column. Samples and standards of 50 mL each were
collected. Within 15 minutes after passage of samples and standards
through reduction column, 2 mL N02 buffer-color reagent (concentrated
HCl, sulfanilimide, N-(l-napthyl) ethylenediamine dihydrochloride and
sodium acetate) were added to each. After 10 minutes of color
development, absorbence was measured at 540 nm using a double beam

spectrophotometer (American Public Health Association 1985).

14

Well homogenized samples and standards (50 mL each) were
transferred to 100 mL Kjeldahl flasks and 10 mL of sulfuric
acid-mercuric sulfate-potassium sulfate solution were added to each for
organic Kjeldahl nitrogen analysis. Prepared samples and standards were
placed on the digestion apparatus in a laboratory fume hood. The water
was allowed to evaporate until white cloudy fumes of 803 were given off.
The digestion was allowed to take place for another 30 minutes. After
flasks were cooled, 30 mL of deionized water were added to each flask to
dissolve the caked material. All samples and standards were distilled
with 10 mL sodium hydroxide-sodium thiosulfate solution using a micro-
Kjeldahl distillation apparatus. Fifty milliliter Erlenmeyer flasks,
each containing 5 mL boric acid, were used to collect 35 mL of
distillate during 'up' position and 10 mL of distillate during 'down'
position. Collected distillate was diluted to 50 mL with deionized
distilled water before 2 mL of Nessler reagent were added. After 20
minutes, absorbence was measured at 425 nm against a deionized distilled
water reference (American Public Health Association 1985).

Five hundred milliliter samples, collected from ponds, were
filtered through 0.80 micron membrane filters. Chlorophyll was
extracted by grinding the filters in about 10 mL of 90% alkaline aqueous
acetone in a tissue grinding tube. Samples were then centrifuged at 3500
rpm until supernatant was clear. Absorbance of the supernatant was read
at 665 and 750 nm. Samples were then acidified by adding 2-3 drops of
4N HCl and the absorbsnce was again measured at 665 nm and 750 nm.
Chlorophyll 2 was calculated according to the following equation

(American Public Health Association 1985):

15

26.7 (665° - 6653) x v
V'x L

where: 6650 is (absorbance at 665 nm before acid) - (absorbance at 750

Chlorophyll 2 (mg/m3) -

 

nm before acid), 665a is (absorbance at 665 nm after acid) - (absorbance
at 750 nm after acid), v is volume of acetone for extraction (mL), V is
volume of water filtered (liters), L is pathlength (cm).

Primary productivity of phytoplankton was determined by measuring
changes in dissolved oxygen in light and dark bottles filled with water
taken from 0.25 m and 0.50 m depths from the center of each pond. The
tube from a Van Dorn water sampler was inserted to the bottom of 300 mL
biological oxygen demand bottles, and bottles were flushed continuously
for three times as long as it took to fill them initially. Bottles were
immediately stoppered and stored in light proof wooden boxes until
further treatment. One bottle from each depth in a pond was fixed
chemically according to the Winkler method with azide modification
(American Public Health Association 1985) to determine the initial
concentration of oxygen. Two bottles (one light and one dark) for each
depth in a pond were then incubated at the same depth where water
samples were taken for a period of 3-4 hours. The incubation was
terminated by immediate chemical fixation of dissolved oxygen as the
bottles were retrieved. The oxygen concentrations were determined by
titrating water samples with 0.005N sodium thiosulphate. I

Phytoplanktonic productivity was calculated according to the
following equations (Wetzel and Likens 1979; Cole 1983):

(LB-DB) x 1000 x 0.375
PQ x t

(LB-TB) x 1000 x 0.375
’PQ x t

 

Gross productivity (mg C/m3/hr) -

Net productivity (mg C/m3/hr) -

 

16
where LB is concentration of oxygen in light bottle, DB is concentration
of oxygen in dark bottle, 13 is concentration of oxygen in initial
bottle, PO is photosynthetic quotient (assumed to be 1.2), t is hours of
incubation, 1000 is number of liters in 1 m3, and 0.375 is molecular
weight ratio of carbon to oxygen gas (02). Net primary productivity was
also estimated by subtracting total inorganic carbon at dawn from total
inorganic carbon at dusk.

Fishes were sampled four times during the grow-out period of 352
days. Ponds were drained to about 20-30 cm depth and fishes were caught
using a seine. At least 10% of each species of the fish stocked were
sampled for measurements of weight, and total and standard length.
Fishes were measured as soon as they were caught and released back into
the water with the least stress possible. Ponds were then refilled to 1
m depths. After 352-day grow-out period, all ponds were drained and
fishes were harvested. Statistical analysis using ANOVA with Duncan's
Multiple Range test was performed on phytoplankton and fish data to

determine significant differences between treatments at p < 0.05.

ALGAL BIOASSAY EXPERIMENT

A series of nutrient bioassays was conducted on waters from
reference ponds, TSP treatment ponds and TSP-urea treatment ponds.
Tests were run on a weekly basis for 7 weeks in January and March 1987
to identify algal growth limiting nutrients in different treatments, and
to attempt to correlate the chemistry of the pond waters with their

ability to support algal growth.

17

All glassware used during this experiment was sterilized to make
sure that cultures were axenic. Water samples were collected in the
morning from one pond from each treatment and were filtered through 0.45
micron membrane filters to remove micro-organisms. Membrane filters
were prewashed by filtering approximately 50 mL of deionized water.
Assays were carried out in 500 mL Erlenmeyer flasks each containing 100
mL of filtered pond water. Additions of carbon (as NaHCO3), nitrogen (as
NaNOg) and phosphorus (as KZHPoa) were made to flasks according to the

following design:

Treatment No. of Replicates
1. Pond water control 3
2. Pond water + 0.05 mg P/L 3
3. Pond water + 1.00 mg N/L 3
4. Pond water + 10.00 mg C/L 3
5. Pond water + 0.05 mg P/L + 3
1.00 mg N/L
6. Pond water + 0.05 mg P/L + 3

1.00 mg N/L + 10.00 mg C/L

7. Pond water + 5% Bold's medium 3

5212222222 2221122122222 Printz, a selected and tested species of

algae well suited to bioassay research (U.S. EPA 1971, Payne 1975), was
used in bioassays. S, 2223122rn2§22 (pure culture was obtained from
Carolina Biological Supply Company) was grown in Bold's Basal Medium as
described in Johnson et a1. (1970) for 7 days. The algae culture was

then centrifuged and the supernatant was discarded. The algae were

18
suspended in sterilized deionized water and again centrifuged to get rid
of excess nutrients. Finally the sedimented algae was resuspended in
sterilized deionized water and used as inoculum for cultures. Cell
counts of the inoculum were made using hemocytometer in order to
determine the volume of the inoculum used for cultures.

All flasks containing pond water and appropriate nutrients were
then inoculated to generate a starting concentration of 103 cells/mL.
Flasks were loosely covered with aluminum foil and incubated for 7 days
in a temperature-controlled room at 24°C 3 2°C under continuous cool
white fluorescent lighting of 4300 lux 1,10 percent measured adjacent to
the flask at the liquid level (U.S. EPA 1971). Culture flasks were
shaken once a day to resuspend algae cells. Determination of algae
growth was accomplished by cell count using a haemocytometer. Specific

growth rates (u) were calculated from:

ln(X2/X1)
u - _________ clays"1

t2 ' t1
where X1 is cells/mL at the beginning of incubation period, X2 is
cells/mL at the end of incubation period, and t2 - t1 is elapsed time in
days for incubation (U.S. EPA 1971). Statistical analysis using ANOVA
with Duncan's Multiple Range test was performed on the.bioassay data to

determine significant differences between treatments at p < 0.05.

19

CHARACTERISTICS OF THE STUDY SITE

This experiment was conducted at the Agriculture University of
Malaysia at Serdang: 101° 42'E, 3° 02'N, at an elevation of
approximately 31 m above mean sea level. This location is in Peninsular
Malaysia which extends from latitude 1° 15' N to 6° 45' N, and from
longitude 99° 35' E to 104° 20' E. With a maximum length of 736 km and
maximum width of 320 km, Peninsular Malaysia covers an area of 13.2
million ha. Peninsular Malaysia is a hilly country with only 30% of its
land suitable for agriculture. Its topography is mainly influenced by
the Main Range which runs from north-west to south-east and reaches an
elevation of about 2400 m above sea level. Like most countries in the
tropics, Peninsular Malaysia experiences high rainfalls and
temperatures. Generally, the east coast of Peninsular Malaysia receives
heavy rainfall in November to March brought by north-east monsoon winds.
The west coast receives rain from southwest monsoons from May to
September. Rainfall ranges from 2000 - 3500 mm/yr. In addition to high
rainfall, Malaysia has high temperatures: they range from 21°C to 34°C.
High temperature and rainfall in Malaysia speed the processes of soil
weathering and leaching. About half of the area in Peninsular Malaysia
is covered by granite and other igneous rocks, one third by stratified
rocks older than granite, and the rest by alluvium. Leaching is said to
be the main mechanism in inducing acidity in soils in this region
(Yaacob and Shamsuddin 1982). Much of the soil in Peninsular Malaysia
is acidic in nature having pH less than 5.0. Base saturation is low and

kaolinite content is high.

20
A major part of Peninsular Malaysia lacks carbonate-rich bedrocks.
The carbonate-containing limestone deposits are restricted regionally to
the northwest and central part of the peninsula. Due to predominance of
igneous rock and high rates of weathering and erosion, nutrient content
of soil and water is low. Because of low bicarbonate content, 90% or
more of the Malaysian fresh water ecosystems can be classified as soft

water and possess little buffering capacity (Yaacob and Shamsuddin

1982).

RESULTS

FIELD DATA

The study area received 2167 mm of rainfall in 1986. Monthly
rainfall ranged from 36 mm to 394 mm. The driest months were February,
June, July, August and September when rainfall was less than 100 mm
(Table 2). Evaporation ranged from 95 mm/month to 152 mm/month with the
highest rates occurring during the June-September interval (Table 2).
Relative humidity was relatively constant throughout the year with
values ranging from 92.43 to 95.7%.

Mean daily minimum and maximum air temperatures during the
experiment are shown in Table 2. Mean minimum temperature ranged from
21.0°C to 23.3°C whilst mean maximum temperature ranged from 31.0°C to
34.0°C. Windspeed at the experimental fish ponds ranged from 0.70 -
1.23 m/sec with the highest values coinciding with the dry season (Table
2).

Water temperature of the experimental fish ponds ranged from 27.4°C
to 33.7°C with maximum diurnal fluctuation of 4.0°C. In early mornings,
pond temperatures were generally vertically uniform throughout the water
column. Surface temperature increased rapidly during days reaching
maximum values in late afternoons. ‘

Mean dissolved oxygen ranged from 4.0 to 14.0 mg/L. Ponds which 7

received fertilizer input exhibited higher mean oxygen concentrations

21

22

 

 

8.8 8.8 86 8.8 8.88 868 8. 8:
8.8 8.8 86 8.8 84.8 848 8. .84
8.8 8.8 84 8.8 848 868 8. .8:
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8.8 8.8 86 8.8 8.84 8.8 8. «:8
8.8 8.8 84 8.8 8.84 8.88 8. 8:
8.8 8.8 86 8.8 8.84 848 8. .8
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23
(Table 3) and fluctuations than ponds which did not. Similar to
vertical temperature profiles, dissolved oxygen concentrations were more
or less uniform vertically at dawn, but became less so during the day as
oxygen in the upper 0.5 m increased at a more rapid rate than in bottom
layers.

The experimental ponds had low alkalinity. Mean total alkalinity
ranged from 15.3 to 29.6 mg CaCO3/L in reference ponds. Values, however
were higher in TSP and TSP-Urea treatment ponds ranging between 16.5 to
35.4 mg CaCO3/L and 14.1 to 36.4 mg CaCOS/L respectively. Due to the
low alkalinity, and thus low buffering capacity of pond water, pH
increased significantly with increased phytoplankton productivity during
days. Mean conductivity values were highest in TSP-urea treatment ponds
followed by TSP treatment ponds and reference ponds (Table 3).

Mean pH ranged from 6.6 to 7.2 in reference ponds, 6.6 to 8.9 in
TéP treatment ponds and 7.0 to 9.8 in TSP-urea treatment ponds. Mean
values during the study period are shown in Table 3. pH was lowest at
dawn and increased to maxima in afternoons. Diurnal change of pH was
highest in TSP-urea treatment ponds followed by TSP treatment ponds. In
reference ponds, diurnal pH increases and fluctuations were much smaller
than in fertilized ponds.

Generally, light did not seem to be limiting in these experimental
ponds. On most sampling dates, light was more than 1% of its.surface
intensity at pond bottoms. Mean light attenuation coefficient was.less
usually less than 4.0, except on days with heavy rain. Then, light
'extinction coefficients in ponds reached mean values of more than 6.0

due to input of silt from stream water and from bank erosion.

24

 

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25
Phytoplankton did not appear to limit light for photosynthesis through
the depth of these shallow ponds. Steemann Nielsen (1962 in Moss 1973)
suggested that chlorophyll 3 of approximately 300 mg/m2 was the maximum
concentration that can be sustained within euphotic zones without
serious limitation on phytoplankton growth by self-shading. Laws and
Malecha (1981) suggested that l-m deep ponds should maintain chlorophyll
9 concentrations of less than 200 mg/m3 to prevent light limitation to
phytoplankton growth rates. In this experiment, the highest mean
chlorophyll 5 concentration was much less than these critical values.
0 Three ponds were used for each treatment in this experiment.
However, only two ponds from the TSP-urea treatment were used for data
analysis because the third one was distrupted by an accident
introduction of tilapia. Table 4 shows that the rate of fish growth was
highest in ponds treated with both phosphorus and nitrogen fertilizer,
with growth rates of 3.6, 2.5 1.1 and 0.9 g/day for A. n991119, 9.
199115, 9. 991919 and 2. g9ni9n9599, respectively, during the 352 day
grow-out period. The growth rates were lower in ponds treated with
phosphorus alone. Under this treatment, A. 9991119, Q. 199119, I.

g9ni9n959§ and Q. 991919 grew at rates of 2.0, 1.7, 0.6 and 0.4 g/day,

respectively. Reference ponds had the lowest fish growth rates of 0.7,
1.2, 0.2 and 0.3 for 5. 9991119, 9. 199119, 3. 3991999993 and 9. 991919,
respectively. Figure 1 further illustrates that ponds treated with both
phosphorus and nitrogen produced the highest yield followed by
phosphorus treatment ponds, and finally reference ponds for all types of

fish. Total net production per 352 day grow-out period were 1713 kg/ha,

26

 

 

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700 m TSP ?
m TSP-urea /
soc - /
500 -‘ /

 

Net Fish Production (kg/ho)

 
  
  
  
    
    

 

 
      
 

O

O
A

 

O
O

A

  

O

 
   
  
   
  

O
O

O
O

9.

k

.
eze
.A

    

 

 

 

 

 

 

  
 

 

 

 

 

_A_. nobills 9. idello f. gonionotus _C. comic

 

Figure 1. Net fish production for _Az. 31331113, 9. idella, g. ggnionotus
and Q. 'carp‘io during 352 day grow-out period in reference, TSP
and TSP-urea treatment ponds. TSP is triple super phosphate.

28
1034 kg/ha and 437 kg/ha for TSP-urea, TSP and reference ponds
respectively. These differences were significant at p < 0.05 (Table 5).

Mean gross primary productivity as estimated by the light-dark
bottle oxygen method was 0.09, 0.17, and 0.26 g C/m2/hr and mean net
productivity was 0.08, 0.12 and 0.21 g C/mz/hr for reference, TSP and
TSP-urea ponds, respectively (Table 5). Net primary productivity was
also estimated by calculating the change of total inorganic carbon
between dawn and dusk. Change of total inorganic carbon was 1.04, 1.48
and 2.41 g C/mZ/day for reference, TSP and TSP-urea ponds respectively,
(Table 5). Assuming an average 12 hour day period for the site, values
for net primary productivity estimated by the oxygen method were 0.96 g
C/m2/day for reference ponds, 1.49 g G/mz/day for ponds receiving
phosphorus input, and 2.47 g C/mz/day for ponds receiving phosphorus and
nitrogen input. These productivity values were closely related to the
rate of change of total inorganic carbon with correlation of r2 - 0.92
(p < 0.05).

Phytoplankton biomass in terms of chlorophyll 9 was found to be
highest in ponds in which both phosphorus and nitrogen fertilizer were
added, with a mean value of 109.18 mg/m3. Ponds which received
phosphorus fertilizer alone had a mean chlorophyll g of 46.71 mg/m3.
Reference ponds exhibited the lowest chlorophyll g with a mean value of
12.50 mg/m3. The differences between treatments were significant (p <
0.05) (Table 5).

- Figure 2 shows the fluctuations of chlorophyll 9 during the study
period. Chlorophyll g in TSP-urea ponds was lower than that in TSP

ponds at the beginning of the experiment, but thereafter increased and

29

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150
150 ..
140 A
130 '-
120 d
110 -
100 d
90-
80-
70-1
60-
50~
40-4
30-'
20-

Chlorophyll 9_ (mean mg/m’)

 

1 0 “ u
u i:
O .

26-Jun

Figure 2.

I Rafaren on
+ TSP

O TSP-urea

.. :: r

 

I r I T

28—Jon

T I U

24-Feb
1987

1 f; 1 l
09-Jul 1 5-Jon IO-Fab

1986

II I I '
08-Apr 21—Apr

Mean concentrations and fluctuations of chlorophyll §_in re-
ference, TSP, and TSP-urea treatment ponds during 1986 and

1987. TSP is triple super phosphate. Broken lines indicate
break in sampling time.

31
remained higher than TSP ponds. Peak concentrations of chlorophyll a in
the TSP-urea treatment coincided with dry months of July 1986 and
February 1987 (Figure 2 8 Table 2). Peak concentrations of chlorophyll
a in TSP treatment ponds occurred during the second week after monthly
additions of phosphorus fertilizer.

Regression analyses of net fish production and primary
productivity, as well as net fish production and chlorophyll 5, revealed
relatively high positive correlations between these parameters. Figure
3 illustrates the relationship between net fish production and gross
primary productivity (r2 - 0.80; p < 0.05). Net fish production was
correlated to net primary productivity with r2 - 0.84 (p < 0.05; Figure
4). Daily change in total inorganic carbon was also a relatively good
estimator of fish yield. Net fish production correlated to it with r2 -
0.86; p < 0.05; Figure 5). In addition, fish production was closely
related to chlorophyll a as shown in Figure 6: the correlation
coefficient r2 was 0.95 (p < 0.05).

Table 6 shows the mean values of phosphorus and nitrogen
concentrations in all treatment ponds. Reference ponds had the lowest
orthophosphate-P concentrations whilst the TSP treatment ponds had the
highest. Orthophosphate-P was present in minute quantities on most
sampling dates for both reference and TSP-urea treatment ponds (Figure
A-l). In TSP treatment ponds, total phosphorus and orthophosphate-P
concentrations were highest during the first four days after fertilizer
was added. In this treatment, high initial total phosphorus and
orthophosphate-P concentrations declined rapidly to pretreatment levels

during the second week after fertilizer was added. Thus, fluctuations

32

 

1900
1000 -
1700 -
1000 -
1500 -
1400 -
1300-
1200 H
1100 d
1000 -
900 -
800 -1
.700 -
000 ~
500

Net Fish Production (kg/ho)

 

400

0.08

Figure 3.

d I
R
300 r

H-

 

y - 5253.0 (1) + 104.2

r’ - 0.00

 

T l

0.32

l r l I

I I T T 1
0.12 0.1 0 0.20 0.24 0.25
Gross Primary Productivity (mean 9 C/mz/hr)

Linear regression analysis of net fish production and gross
primary productivity in experimental ponds during 1986 and
1987. R is reference, T is TSP treatment and TU is TSP-urea
treatment. TSP is triple super phosphate.

33

 

1000
1700 d
1600 -
1500 -
1400 -‘
1300 -‘
1200 -‘
1100 -'
1000 -
900 -1
000 -‘
700 -‘
000 -‘
500 '1
400

Not Fish Production (mean kg/ha)

 

H.

 

y - 7130.7 (11) + 3.1

r2 - 0.04

 

300
0.07

Figure 4.

 

i T i i i

T l I I
0.09 0:11 0.13 0.15 0.17 0.19 0.21 0.23 0.25
Not Primary Productivity (mean 9 C/mz/hr)

l l i 1

Linear regression analysis of net fish production and net
primary productivity in experimental ponds during 1986 and
1987. R is reference, T is TSP treatment and TU is TSP-urea
treatment. TSP is triple super phosphate.

1800

34

 

1700 -
1000 a
1500 J
1400 a
1300 a
1200 ~
1100 a
1000 +
900 q
000 -
700 1
000 ~
500 -
400 -

Not Fish Production (kg/ha)

 

an

4-

    

y - 823.2 (x) - 301.8
- rA-1100

 

 

300
0.8

Figure 5.

I i r r r I r r I n 1 1 I i
1.0 1.2 1.4 1.8 1.8 2.0 2.2 2.4 2.6

Change in Total C02 (mean 9 C/mz/day)

I

Linear regression analysis of net fish production and daily
change in total inorganic carbon in experimental ponds dur-
ing 1986 and 1987. R is reference, T is TSP treatment and
TU is TSP-urea treatment. TSP is triple super phosphate.

35

 

1900
1000 -
1700 d
1000 d
1500 j
1400 -
1300 -
1200 -
1100 4
1000 d
900 -
800 -
700 -
600 -
500 -
400 d

Net Fish Production (kg/ha)

 

as

'4.

y - 13.0 (x) + 344.3
rz- 0.00

 

 

300

Figure 6.

I T I I I I I T I

I
20 40 00 80 100 120
Chlorophyll a (mean mg/ma)

Linear regression analysis of net fish production and chloro—
phyll a concentration in experimental ponds during 1986 and
1987. R is reference, T is TSP treatment, and TU is TSP-urea
treatment. TSP is triple super phosphate

36

 

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37
in phosphorus concentrations were great in TSP treatment ponds (Figures
Al & A2). TSP-urea treatment ponds, which received smaller doses of
fertilizer weekly, maintained more constant phosphorus concentrations
throughout period of sampling.

Mean nitrate+nitrite-nitrogen, total ammonia nitrogen and organic
KJeldahl nitrogen were highest in TSP-urea treatment ponds, followed by
reference ponds and TSP treatment ponds, respectively. The differences
between concentrations of nitrogen forms in TSP and reference ponds were
small (Table 6). Nitrate+nitrite concentrations was always low in both
TSP and reference ponds except toward the end of the study period when
slight increases were observed. In TSP-urea ponds, nitrate+nitrite
nitrogen concentrations tended to increase during the study and reached
maximum concentrations at the end of the experiment (Figure A-3). Total
ammonia nitrogen concentrations were consistently higher than
nitrate+nitrite nitrogen concentrations for all treatment ponds (Table
6). Total ammonia nitrogen concentrations in reference ponds were

generally higher than in TSP ponds (Figure A-h).

BIOASSAY RESULTS

Effects of various nutrient additions relative to control cultures
on growth of S. canniggxnuggn in pond waters are shown in Figures 7
through 9. Nutrient concentrations in pond water used in bioassays and
concentrations in bioassay flasks following nutrient additions are given
in Tables 7 through 9.

With water from reference ponds, addition of 0.05 mg P/L always

resulted in a stimulation of algal growth rate. However, the degree of

 

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24

Reference

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PW is pond water, P

is phosphorus, N is nitrogen, C is carbon, Bold's is Bold's

Effects of various nutrient additions on the growth of S.
basal medium, and TSP is triple super phosphate.

treatment ponds on March 17, 1987.

Figure 7.

 

 

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PW is pond water, P is

phosphorus, N is nitrogen, C is carbon, Bold's is Bold's

. basal medium, and TSP is triple super phosphate.

Effects of various nutrient additions on the growth of S.
treatment ponds on March 24, 1987.

Figure 8.

Specific Growth Rate/day

40

 

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Figure 9. Effects of various nutrient additions on the growth of S.
capricornutum in water from reference, TSP and TSP-urea
treatment ponds on March 31, 1987. PW is pond water, P
is phosphorus, N is nitrogen, C is carbon, Bold's is Bold's
basal medium, and TSP is triple super phosphate.

 

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44

response to phosphorus was variable depending on the concentration of
inorganic nitrogen at the time water was collected for bioassay. If
inorganic nitrogen was low, the addition of both phosphorus and nitrogen
resulted in significantly (p < 0.05) higher specific growth rate than by
the addition of phosphorus alone (Figure 7). When the inorganic
nitrogen to orthophosphate-P ratio in source water was approximately
12:1 (Table 7), the algae specific growth rate increased from 0.68/day
to 1.05/day with the addition of phosphorus, and approximately doubled
when both phosphorus and nitrogen were added together (Figure 7).
However, if the inorganic nitrogen concentration was high in source
water, addition of phosphorus and nitrogen together stimulated the
growth rate only slightly over that obtained by addition of phosphorus
alone. Tables 8 and 9 show that when inorganic nitrogen-
orthophosphate-P ratios were 188:1 and 412:1, the differences in growth
rates caused by the addition of phosphorus alone and addition of both
phosphorus and nitrogen were trivial (Figures 8 & 9). Nitrogen
enrichments stimulated small growth'response in reference pond water.
Carbon was not limiting in reference pond bioassays as addition of
inorganic carbon to the culture did not stimulate further growth beyond
that in cultures without carbon addition (Figures 7-9). Specific growth
rates in Bold's medium was always highest indicating that a growth
factor other than phosphorus, nitrogen or carbon was absent in pond
water but present in the medium.

In bioassays from TSP treatment, specific growth rate in the
control culture was higher than the control culture of reference ponds

(Figures 7-9). Phosphorus enrichments did not stimulate a response in

45

bioassay cultures in this series (Figures 7 & 8), except when pond water
was low in phosphorus (Table 9, Figure 9). Additions of nitrogen on the
other hand, always significantly increased algae growth rates (p < 0.05).
In this water, additions of phosphorus and nitrogen together did not
show significant differences in growth rates from additions of nitrogen
alone (p > 0.05: Figures 7 & 8), except in the bioassay series shown in
Figure 9. For this series, phosphorus and nitrogen concentrations were
both low (Table 9) and addition of phosphorus and nitrogen together'
resulted in significantly better response than each nutrient alone (p <
0.05). As in reference pond bioassays, inorganic carbon enrichment did
not show additional algae growth in TSP bioassay cultures. Bold's
medium stimulated the highest algae growth rates illustrating the
presence of growth factor other than phosphorus, nitrogen or carbon.

In TSP-urea bioassays, algae specific growth rates in control
culture flasks were always higher than growth rates in controls of TSP
treatment cultures (Figures 7-9). In this series, phosphorus
enrichments always resulted in positive algae growth responses. The
degree of response however, was highly dependent on phosphorus
concentration in the source water. Growth response was higher relative
to control when phosphorus in the source water was low: that is, when
inorganic nitrogen-phosphorus ratios were high (Figures 7 & 9, Tables 7
& 9). Additions of P and N together did not result in significantly
higher growth response from addition of phosphorus alone (p > 0.05;
Figures 7 & 8). Enrichment with phosphorus, nitrogen and inorganic

carbon did not change the growth response from that obtained with

46
phosphorus and nitrogen alone. Adequate quantities of inorganic carbon

were apparently present in source water.

DISCUSSION

Fish ponds fertilized monthly with triple-super-phosphate, as
recommended by the Malaysian Fisheries Department, were compared to non-
fertilized ponds (reference treatment) and ponds treated weekly with
triple-super-phosphate plus urea. Net fish production increased from
437 kg/ha in reference ponds to 1034 kg/ha in TSP treatment ponds. The
highest production of 1713 kg/ha was recorded in TSP-urea treatment
ponds. A significant increase in fish production observed in TSP-urea
treatment ponds indicated that weekly addition of phosphorus and
nitrogen fertilizers promoted fish above that obtained by monthly
addition of phosphorus fertilizer alone.

The highest growth rates for all species of fish used were observed
in ponds treated with phosphorus and nitrogen fertilizers, indicating
that more food was available in this treatment than in the others. The
fastest growing fish was the plankton and detritus feeder, big head carp
(Axiggighghxg nobilia). It grew at rate of 3.6 g/day in ponds enriched
with both phosphorus and nitrogen fertilizer. Fry and adults of this
fish feed on zooplankton as well as phytoplankton (Hora and Pillay
1962). In TSP treatment ponds, big head carp grew at rate of 2.0 g/day:
the highest among the four fishes used. However, it grew at rate of
only 0.66 g/day in reference treatment ponds where chlorophyll a and

phytoplankton productivity were lowest of all treatments.

47

48

The grass carp, gggggphggynggg9341ggllg was the second fastest
growing fish under these treatment conditions. It grew at rate of 2.5
g/day in TSP-urea treatment ponds, 1.7 g/day in TSP treatment ponds and
1.2 g/day in reference ponds. Adults of this fish eat a-wide range of
higher plants (Scott and Robson 1970) and are known to consume detritus
and benthos if aquatic plants are absent (Terrell and Terrell 1975).
Their flexible feeding habits appear to account for their growth in
ponds in this experiment where little or no vegetation occurred.

The growth of common carp, figuring; garnig was relatively slow in
this experiment. Its growth rates were 1.1 g/day, 0.6 g/day and 0.3
g/day in TSP-urea treatment, TSP treatment and reference ponds
respectively. Main food items in the diet of common carp are benthos
and detritus (Hora and Pillay 1962; Cohen et a1. 1983). Since these
experimental ponds were new, benthic organisms were very poorly
developed (Hustafa Kamal, in preparation). This and competition for
food with other fishes appeared to account for very poor growth by this
benthic feeder.

The herbivore, £33313; ggnigngtgg demonstrated the slowest growth
rate among the four types of fish used in all treatments. Being a
herbivore whose main food is aquatic vegetation and grasses,_£.
3231939335 was likely in competition for sparse food resources with
grass carp. Hora and Pillay (1962) reported that 2. 3931239535 is a
slow growing fish attaining weight of 250 - 500 g at the end of first
year in manured ponds. Data from this experiment show that it was not a
suitable polyculture component with pond management procedures that were

used. There was not enough development of macrophytes due to heavy

49
grazing by the herbivores. Silver carp flypgphghglmighghyg mglitgix
Val., whose food preference is mainly phytoplankton (Cohen et a1. 1983),
would fare better in this polyculture system as there was plenty of
phytoplankton as indicated by high standing crop of chlorophyll a,
especially in TSP-urea treatment ponds. However, in practice Malaysian
fish farmers usually provide tapioca leaves (flgnihgg utiligfiing) and
napier grass (fignigggym ngxpgggn) as supplemental feeding such that food
is available for herbivores, like 2. ggnignggug and Q. 1ggllg.

Results show that gross and net primary productivity and
chlorophyll a in TSP treatment ponds were significantly higher than in
reference ponds, but were significantly lower than in TSP-urea ponds.
Ponds bearing the highest primary productivity supported the highest
fish production and those with the lowest primary productivity supported
the lowest fish production, suggesting a close relationship between
algal productivity and fish yield. Regression analyses revealed that
fish net production was closely related to primary productivity and
algae biomass. In this study, polyculture net production was
significantly related to light-dark bottle gross primary productivity
(r2 - 0.80, p < 0.05), net primary productivity (r2 - 0.84, p < 0.05),
change in total inorganic carbon (r2 - 0.86 p < 0.05) and chlorophyll a
(r2 - 0.95, p < 0.05). Other researchers have reported similar results
with fertilizers and fish that feed largely on the first trophic level.
Melack (1976) and McConnell et a1. (1977) found close relationships
between fish production and primary productivity. Almazan and Boyd
(1978) reported that yields of 1113215 sung; were related to chlorophyll

a with r - 0.89, and to light-dark bottle productivity with r - 0.79.

50
Liang et a1. (1981) reported that yields of silver carp and bighead carp
were related to gross productivity with r2 - 0.76.

The quantity and rate of primary production in treatments in this
experiment was related to the amount of the limiting nutrients available
in pond water. Hutchinson (1967) stated that the concentration of
combined nitrate and phosphate was more likely to determine the quantity
of phytoplankton than any other factor. Kean net primary productivity
of the reference treatment was estimated at 1.04 g C/mZ/day and mean
chlorophyll g was 12.50 mg/m3 respectively. These values were
significantly lower than those obtained from TSP treatment ponds.
Comparing nutrient availability in reference and TSP treatment ponds
showed that on average, the former had lower phosphorus concentrations,
but slightly higher nitrogen concentrations than the latter. Data
suggests that reference ponds experienced phosphorus shortages leading
to the low phytoplanktonic productivity observed in this treatment.

An analysis of nutrient concentrations in ponds as compared to
amounts of nutrients required by algae to complement daily rates of
photosynthetic carbon fixation is given in Table 10. In the reference
treatment the supply of inorganic nitrogen present in ponds was adequate
to meet algae needs, but phosphate phosphorus was in very short supply.
The inorganic nitrogen to orthophosphate-P ratio was 36. This high
ratio indicates that orthophosphate-P concentration was low relative to
inorganic nitrogen in the reference treatment. That phosphorus
limitation occurred in reference ponds is supported by Chiaudani and
Vighi (1974, 1975) who reported that a total inorganic nitrogen to

orthophosphate-P ratio by weight higher than 10 was an index of

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52
phosphorus limitation. Green et al. (1976) considered waters containing
a total inorganic nitrogen to orthophosphate-P ratio greater than 11.3
to be phosphorus limited for algal growth. Weiss (1976) found that
waters with inorganic nitrogen to orthophosphate-P ratio of about 28 to
be phosphorus limited.

Phosphorus limitation in reference ponds was further supported by
the bioassay experiment. Addition of phosphorus to water from these
ponds increased algal growth in bioassay cultures. However, addition of
phosphorus to reference pond water containing inorganic nitrogen and
orthophosphate-P in the ratio of 12:1 increased algal growth less than
when both phosphorus and nitrogen were added. This indicated that when
phosphorus and nitrogen were both low in supply, the addition of
phosphorus alone quickly limited the supply of nitrogen. This
interpretation of results is consistent with the work of Maloney et a1.
(1972) who found that waters with low phosphorus and nitrogen
concentrations (0.001 mg/L of orthophosphate and 0.034 mg/L inorganic
nitrogen) showed higher growth response to enrichment of both phosphorus
and nitrogen together than to phosphorus alone. Miller et a1. (1974)
reported similar bioassay results in soft waters of low and moderate
productivity. They concluded that phosphorus was initially limiting for
algal growth, but nitrogen and perhaps carbon became limiting once
sufficient phosphorus was present. Payne (1975) in reviewing response
of bioassay cultures using natural waters showed that incremental
additions of phosphorus results in corresponding increases in
figlgngfigrnn growth from 0.001 to 0.010 mg P/L. Above this

concentration, growth response ceased as nitrogen became limiting.

53

Reference pond water for bioassays collected during the last two
weeks of March 1987, contained relatively high inorganic nitrogen
concentrations such that ratios of inorganic nitrogen to orthophosphate-
P were 188:1 and 412:1. Addition of phosphorus alone to this water
promoted rapid algae growth almost similar to that when both phosphorus
and nitrogen were added. Growth of algae in pond water enriched with
nitrogen was the same as in pond water control cultures. Therefore,
nitrogen alone did not promote algal growth. Non-utilization of
nitrogen without phosphorus addition explained consistently higher
ammonia concentration observed in reference ponds as compared to TSP
treatment ponds. This phenomenon was also reported by Zeller (1952) who
found higher concentrations of inorganic nitrogen in unfertilized than
fertilized ponds. He attributed the low values in fertilized ponds to
phytoplankton activity.

Regarding the TSP treatment, orthophosphate-P was present in ponds
in a quantity close to that required to complement photosynthetic carbon
fixation, but inorganic nitrogen was in short supply (Table 10).
Nitrogen shortages in TSP treatment ponds was also reflected in a low
ratio of inorganic nitrogen to orthophosphate-P (a ratio of 2),
indicating that phosphorus was more available for phytoplankton uptake
relative to nitrogen (Table 10). Miller et a1. (1974) reported similar
findings: that lake waters with high concentrations of orthophosphate-P
were likely to become limited by nitrogen or some other nutrient. They
further demonstrated that productive soft waters with inorganic nitrogen
to orthophosphate-P ratios between 2 to 5 were nitrogen limited.

Chiaudani and Vighi (1974) reported that a ratio of total inorganic

54
nitrogen to orthophosphate-P of less than 5 reflects nitrogen
limitation. DeNoyelles and O'Brien (1978) reported that nitrogen was
limiting in ponds which had inorganic nitrogen to orthophosphate-P
ratios of less than 5.

Bioassay results showed that phosphorus enrichments to pond water
from the TSP treatment did not increase algae specific growth rate more
than the control cultures, except towards the end of the monthly
fertilization regime when phosphorus concentrations in pond water were
low. on the other hand, additions of nitrogen always increased algae
growth rates, indicating nitrogen shortages in ponds in this treatment.
Addition of nitrogen alone was as good as addition of both phosphorus
and nitrogen in TSP treatment bioassays until late in the monthly
fertilization cycle. At this point, enrichment by phosphorus and
nitrogen together was better than each separately, demonstrating that at
times phosphorus was not sufficient even with TSP treatment.

Phosphorus was in short supply relative to algae requirements in
TSP-urea treatment ponds, while inorganic nitrogen was more plentiful
(Table 10).. An inorganic nitrogen to orthophosphate-P ratio of 44
occurred in TSP-urea treatment ponds, suggesting that phosphorus was
limiting. This result is in agreement with that of Maloney et al.
(1972) who observed that an inorganic nitrogen to orthophosphate-P ratio
of above 23 coincided with marked phosphorus limitation. The work of
Chiaudani and Vighi (1974), Miller et a1. (1974) and Weiss (1976)
predicts that waters having inorganic nitrogen and orthophosphate
concentrations in the ratio of 44 will be short in phosphorus supply

relative to algae needs.

55

Bioassay results from TSP-urea pond water cultures supported the
phosphorus shortage hypothesis for this treatment. Addition of
phosphorus always increased algal growth above that obtained for control
cultures. Addition of nitrogen, on the other hand, did not increase the
algal growth rate above that of the control cultures, except when
nitrogen concentrations in pond water was relatively low. Enrichments
of phosphorus and nitrogen together did not greatly stimulate algal
growth above that obtained by phosphorus alone, indicating that nitrogen
was adequate in pond water to meet algal needs. Thus bioassay results
confirmed nutrient shortages suggested for each treatment from field
data (Table 10).

Additions of inorganic carbon to bioassay cultures did not produce
algal growth response in water from any treatment beyond the response
obtained by additions of phosphorus and nitrogen discussed above. This
suggested that pond water used in bioassays had sufficient inorganic
carbon. Conditions in ponds in relation to carbon dioxide were examined
by calculating mean free carbon dioxide for intervals of days from
measurements of alkalinity, pH and temperature. Results are shown in
Figure 10.

For ponds in reference and TSP treatments, free carbon dioxide was
at non-limiting concentrations and above atmospheric equilibrium
concentrations throughout the day. Examining Figure 10, free carbon
dioxide in TSP-urea treatment ponds went below the equilibrium carbon
dioxide concentration at about 1330 hours daily. While algae can
extract free carbon dioxide from water at very low concentrations,

growth rates are depressed below 10 umole/L (King 1970). Data in Figure

 

190

 

 

 

 

 

 

 

 

100
I70
160 -1
130 .4 .
14o - \
Q 130 ., \
a 120 -
‘2 no - \
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TSP and TSP-urea treatment ponds during 1986 and 1987 in
relation to air-water equilibrium.concentrations of carbon
dioxide. TSP is triple super phosphate.

57
10 show that free carbon dioxide tended to be at growth limiting
concentrations in TSP-urea treatment ponds in late afternoon.
Shallowness of the ponds (l m mean depth) and relatively high average
wind speed (1.2 m/sec) favored carbon dioxide flux into pond water, to
support the relatively high phytoplanktonic productivity observed in
this treatment.

High primary productivity in spite of low free carbon dioxide
concentration was also reported by Moss (1973) who attributed decrease
in free carbon dioxide to algal blooms. He explained that high
productivity was however sustained in enriched waters because
unavailability of free carbon dioxide caused replacement of one
population by another more efficient at low free carbon dioxide with
little loss of primary productivity. King (1970) and Shapiro (1973)
suggested that carbon shortage may be involved in changing species
composition to large colonial blue greens in eutrophic waters, since
these organisms were better than their competitors in obtaining carbon
dioxide at low concentration. Dominance of fligrggxggig sp. in TSP-urea
treatment ponds (personal observation) coincide with low free carbon
dioxide. Thus, low availability of free carbon dioxide may not have
limited phytoplankton productivity in TSP-urea treatment ponds, but it
may have influenced the phytoplankton species composition (DeNoyelles
and O'Brien 1978). Control of undesirable blue-green algae under
conditions in these ponds might be accomplished by adding agricultural
limestone to ponds to provide additional inorganic carbon. .

As Boyd (1982) pointed out, liming fish ponds that have low

alkalinity, like those at the experimental site, tends to increase

58
morning pH. However, because of enhanced buffering capacity due to
liming with CaCO3, afternoon pH levels in fertilized ponds tend to
decrease compared to afternoon pH levels prior to liming. Since low
free carbon dioxide concentrations in the experimental ponds were due
largely to the influence of high pH, and low free carbon dioxide levels
promoted blue-green algae, liming ponds with TSP-urea treatment
characteristics may control development of these algae.

It can be seen from the results of this work that weekly addition
of phosphorus and nitrogen fertilizers to new fish ponds at the
experimental site increased primary productivity and fish production
beyond that achieved by monthly addition of phosphorus fertilizer alone.
It is also clear that more experimental attention should be focused on
the interplay between nitrogen, phosphorus and inorganic carbon in
regulating primary productivity and algal biomass in fish ponds. The
disagreement over the necessity of nitrogen as fish pond fertilizer
(Hickling 1962); Boyd and Sowles 1978) will likely continue in Malaysia
until further research demonstrates whether or not nitrogen addition
produces the effect shown here over broad geographical portions of the

country.

LITERATURE CITED

Almazan, G., and C.E. Boyd. 1978. Plankton production and tilapia yield
in ponds. Aquaculture 15:75-77.

American Public Health Association. 1985. Standard Methods for the
Examination of Water and Wastewater. 16th edition. APHA,
Washington D.C. 1134 pp.

Aschner, M., C. Laventer, and I. Chorin-Kirsch. 1967. Off-flavor in
carp from fish ponds in the coastal plain and the Galilee. Bamidgeh
19:23-25.

Ball, R.C. 1949. Experimental Use of Fertilizer in Production of Fish
Pond Organisms and Fish. Michigan State College Argicultural
Experimental Station, East Lansing, Michigan, Technical Bulletin
223. 32 pp.

Boyd, C. E. 1973. Summer algal communities and primary productivity in
fish ponds. Hydrobiologia 41: 357- 390.

Boyd, C.E. 1976. Nitrogen fertilizer effects on production of 1113213
' in ponds fertilized with phosphorus and potassium. Aquaculture
7:385-390.

Boyd, C.E. 1979. Water Quality in Warmwater Fish Ponds. Auburn
University Agricultural Experimental Station, Auburn, Alabama. 395

PP-

Boyd, C.E. 1981. Fertilization of warmwater fish ponds. J. Soil Water
Cons. 36:142-145.

Boyd, C.E. 1982. Water Quality Management for Pond Fish Culture.
Elsevier Scientific Publishing Company, New York. 318 pp.

Boyd, C.E. and Y. Musig. 1981. Orthophosphate uptake by phytoplankton
and sediment. Aquaculture 22: 165- 173.

Boyd, C.E. and J.W. Sowles. 1978a Nitrogen fertilization of ponds.
Trans. Am. Fish. Soc. 107:737-741.

Brook, A.J. 1958. Changes in phytoplankton of some Scottish hill lochs

resulting from the artificial enrichment. Ver. Int. Verein. Theor.
Angew. Limnol. 13:298-305.

59

60

Chiaudani, G., and M. Vighi. 1974. The N:P ratio and tests with
figlgngggggn to predict eutrophication in lakes. Water Research
1063-1069.

Chiaudani, G., and M. Vighi. 1975. Dynamics of nutrient limitation in
six small lakes. Verh. Int. Verein. Limnol. 19:1319-1324.

Cohen, D., Z. Ra'anan and A. Barnes. 1983. Production of freshwater

prawn nagrghxgghign Igggnhgrgii in Israel. 1. Integration into
fish polyculture systems. Aquaculture 31:67-76.

Cole, G. A. 1983. Text Book of Limnology. The C.V. Mosby Company. St.
Louis. 401 pp.

Dendy, J.S., V. Varikul, K. Sumawidjaja, and M. Potaros. 1968.
Production of 111§31§_n9§§gmh195 Peters, plankton, and benthos as
parameters for evaluating nitrogen in pond fertilization. Proc.
World Symposium on Warm-Water Pond Fish Culture, FAO United
Nations, Fish Rep. 44:226-240.

DeNoyelles Jr., F., and W.J. O'Brien. 1978. Phytoplankton succession in
nutrient enriched experimental ponds as related to changing carbon,
nitrogen and phosphorus conditions. Arch. Hydrobiol. 84:137-165.

Dickman, M. and 1.8. Efford. 1985. Some effects of artificial
fertilization on enclosed plankton populations in Marion Lake,
British Columbia. J. Fish Res. Bd. Canada 29:1595-1604.

Dobbins, D.A.,and C.E. Boyd. 1976. Phosphorus and potassium
fertilization of sunfish ponds. Trans. Am. Fish. Soc.
105:536-540.

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APPENDIX

66

 

180
170 4'
180‘
12.50d
”0..
130-
120-1
110-
100-
90-
80-4
70--J
80-1
50~
40-
30-1
20-
10*

0

Orthophosphate-P (119/ L)

 

I Reference
+ TSP

e TSP-urea

 

AA

-—-'__..—-_-_2 .;--__..._ 22‘..—

 

 

1 3-Moy

j

I I a I
28-Moy 01 «Jul 14-Jul 17—Feb 03-Mor 17-Mor 31 ~Mor
1986 1987

r V

Figure A-l. Mean concentrations of orthophosphate-P in reference, TSP

and TSP-urea treatment ponds during 1986 and 1987. TSP
is triple super phosphate.

67

 

340
320 d I Reference
300 -+ , T5,,
280 4
250 J
240 d .
220 - >
200 - :
180 -*
150 4 . .
140 -1
120 - +
100 -
80-4
50 .1
4,0 —1

20 I I I I I T Hi I I ‘l U I V
13-Moy 28-Moy 01-Ju1 1 4—Ju1 17-Feb 03-Mor 17-Mor 31 -Mor

1986 1987

O TSP-urea

Total Phosphorus (ug/ L)

 

 

r

 

Figure A—2. Mean concentrations of total phosphorus in reference, TSP
and TSP-urea treatment ponds during 1986 and 1987. TSP
is triple super phosphate.

68

 

    

 

 

 

 

400
a Reference
350 "" + TSP
e TSP-urea
300'fi
Q -
a! 250
3
f: 200-1
3" ..
3n 150 ~ "
‘z
100 -‘
50 -‘
O 4!? f 3? ' I E“: ' ~ I j I 1 I '
13-Moy za-uay 01-Ju1 14—Ju1 17-Feb 03-Mor 17-Mor 31...“,
1986 1987

Figure A-3. Mean concentrations of nitrate+nitrite nitrogen in reference,
TSP and TSP-urea treatment ponds during 1986 and 1987. TSP
is triple super phosphate.

69

 

300
280 -
280 ..
240 -
220 '-
200 -
180 '-
160 'i
140 -
120 -
100 ..
BO -'
BO '-
40 ..
20 -*

Total Ammonia Nltrogen (ug/ L)

 

4.

O

  
 
  

Reference
TSP
TSP-urea

l3-Moy

Figure A-4 .

r

I
01-Jul

WW

I
1 4-Jlll

r I
17-F6b

I
03-Mor

r

I
1 7-Mor

f

 

31 -Mor

I
28-Moy

1986 1987

Mean concentrations of total ammonia nitrogen in reference,
TSP and TSP-urea treatment ponds during 1986 and 1987. TSP
is triple super phosphate.