“AA—A “g“ Ag .uHWptvPv ~ AN EVALUATION OF THE USE OF ARTIFICIAL SUBSTRATES FOR DETERMINING PRIMARY PRODUCTION IN FLOWING WATER Them for II» Degree 05 M. S. MICHIGAN STATE UNIVERSITY John Chutes PM”: 1959 IlllIIIIZIIIIIIIIIIIIIIIIIIIIIII _ 31293 10459 9372 ‘ AN EVALUATION OF THE USE OF ARTIFICIAL SUBSTRATES FOR DETERMINING PRIMARY PRODUCTION IN FIOWING WATER by John Charles Peters AN ABSTRACT Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 1959 Approved: REILl/ITC\ \g “M JOHN CHARLES PETERS ABSTRACT Artificial substrates, plexiglass plates, were used to estimate primary production in flowing waters. Taxonomic investigation showed that the substrates were not selective. Diatoms were found to be the principal group of organisms collected on the substrates. Three methods were utilized to estimate production (1) the number of organisms per unit area per sampling period; (2) the weight of organic matter per unit area per sampling period; and (3) the amount of phytopigment unit (density of chlorophyll color) per unit area per sampling period. Numeralizations of the relationship between these units were expressed by calculating corre- lation coefficients. The correlation coefficients expressing the relationship between number of organisms and the phytopigment were high, ranging from .75 to .90. A cor- relation coefficient of .93 expressed the numerical relationship between the weight of organic matter and the phytopigment unit . The effect of periodic community changes was consid— ered by comparing individual community regression lines with a common line. The statistical analysis showed a common line could be used to estimate the number of organisms from the phytopigment unit at the sampling site which had the greatest number of individual dominant com- munities and the widest range of units. A common slope JOHN CHARLES PETERS ABSTRACT was found to exist between 5 diatom communities and the phytopigment unit—weight of organic matter relationship. It is possible that a common line can be used throughout most of the year except during low levels of production (winter period) when a lower intercept can be substituted in the predictor equation. A close relationship existed between the rate of solar input and the production of organic matter. The possibility of photo-inactivation from high light inten- sities was considered and rejected. The sampling site which had no shade cover, the lowest nutrient level, and the least stable physical and chemical environmental conditions had the highest level of production. AN EVALUATION OF THE USE OF ARTIFICIAL SUBSTRATES FOR DETERMINING PRIMARY PRODUCTION IN FLOWING WATER by John Charles Peters A THESIS Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 1959 ACKNOWLEDGMENTS The writer extends appreciative gratitude to Dr. Robert C. Ball whose guidance was generously contributed to the study. He is indebted to Dr. Phillip J. Clark and Dr. D. w. Hayne for their advice on statistical analysis; Dr. Gerald w. Prescott and Mr. Phillip Halicki for their aid in diatom taxonomic problems; Mr. Albert Grzenda whose suggestions and comments were helpful throughout the project; and to his wife, Marietta Peters, for her constant encouragement and her drawing skill which is responsible for the figures and charts in the thesis. My participation in the study was made possible through a graduate research assistantship from the Agricultural Experiment Station. TABLE OF CONTENTS INTRODUCTION. . . . . . . . . . . DESCRIPTION OF THE STUDY AREA METHODS AND TECHNIQUES Counts of cells Identification of organisms . Chlorophyll color. . . . . . Organic matter. . . . . . . . . Linear regression and correlation Water temperature. Solar radiation RESULTS AND CONCLUSIONS Qualitative. Quantitative Phytopigment units—number of organisms. Phytopigment units-weight of organic matter Variation in production. . . . . . Solar radiation . . . . . . . . SUMMARY APPENDICES . . . . . . . . . . . . . . A--Daily high and low water temperatures recorded at a station 10 miles upstream from the mouth of the Red Cedar River . . B--Plates showing abundant and rare forms of diatoms occurring in the Red Cedar watershed. Page 12 16 2o 20 2A 27 28 29 30 3o 45 A5 62 66 74 8O 83 84 87 iv APPENDICES Page C-—List of dominant and rare species occurring on natural and artificial substrates in the Red Cedar watershed . . . . . . . . . . 92 D--List of quantitative units in a chronological sequence taken from artificial substrates from 4 stations in the Red Cedar watershed . . . 94 LITERATURE CITED . . . . . . . . . . . . 102 TABLE 10. 11. LIST OF TABLES The Distribution of an Aufwuchs Subsample Deposited on a Membrane Filter Showing a Test for Randomness. List of Dominant Organisms at Each Station on Dates of Occurrence. . . . . . . Comparison of the Regression Coefficients and Correlation Coefficients Expressing the Phytopigment Unit-Number of Organisms Relationship from the Four Sampling Sites Statistical Comparison of Four Correlation Coefficients Taken from the Phytopigment Unit- Number of Organisms Relationship in the Red Cedar Watershed. . . . . . . Covariance Analysis between Regression Lines for Phytopigment Units and Number of Organ- isms for 4 Communities at Station I . . Covariance Analysis between Regression Lines for Phytopigment Units and Number of Organ- isms for 4 Communities at Station III. Covariance Analysis between Regression Lines for Phytopigment Units and Number of Organ- isms for 5 Communities at Station IV . Covariance Analysis between Regression Lines for Phytopigment Units and Number of Organ- isms for 2 Communities at Station V . . Covariance Analysis between Regression Lines for Phytopigment Units and Weight of Organic Matter for 5 Communities at Station IV Analysis of Variance of Three Stations in the Red Cedar Watershed from July 19, 1958 to September 30,1958 . . Duncan's Multiple Range Test Showing Signifi- cant Differences between Station Means in the Red Cedar Watershed from July 19, 1958 to September 30,1958 PAGE 19 33 46 A7 52 55 58 61 65 70 71 TABLE 12. Analysis of Variance of Four Stations in the Red Cedar Watershed from October 1, 1958 to February 8, I959 . . . . . . . l3. Duncan's Multiple Range Test Showing Signifi- cant Differences Between Station Means in the Red Cedar Watershed from October 1, 1958 to February 8, 1959 . . . . . . . 14. The Average Light Intensity Expressed in Gram-Calories per Square Centimeter per Day during Each Sampling Period. vi PAGE 72 73 78 LIST OF FIGURES FIGURE PAGE I. Drainage area of the Red Cedar River and its tributaries. . . . . . . . . . . 6 II. Red Cedar River and sampling stations in the vicinity of Williamston, Michigan . . . 9 III. Plexiglass artificial substrates showing position, method of attachment, and actual size of substrate. . . . . . . 14 IV. Correction graph for adjusting measured phytopigment absorbancy values to units related to concentration . . . . . . 22 V. Flow chart showing procedure for obtaining estimates of organic matter from organisms attached to the substrates. . . . . . 25 VI. Seasonal periodicity of algal organisms which became attached to artificial sub- strates at Station I. . . . . . . . 35 VII. Seasonal periodicity of algal organisms which became attached to artificial sub- strates at Station III . . . . . . . 37 VIII. Seasonal periodicity of algal organisms which became attached to artificial sub— strates at Station IV . . . . . . . 39 IX. Seasonal periodicity of algal organisms which became attached to artificial sub— strates at Station V. . . . . . . . 41 X. The common regression line expressing the phytopigment unit—number of organisms relationship compared with the individual regression lines for 4 communities at Station I . . . . . . . . . . . 50 XI. The common regression line expressing the phytopigment unit-number of organisms relationship compared with the individual regression lines for 4 communities at Station III. . . . . . . . . . . 53 viii FIGURE PAGE XII. The common regression line expressing the phytopigment unit-number of organisms relationship compared with the individual regression lines for 5 communities at Station IV . . . . . . . . . . . 56 XIII. The common regression line expressing the phytopigment unit-number of organisms relationship compared with the individual regression lines for 2 communities at Station V . . . . . . . . . . . 59 XIV. The common regression line expressing the phytopigment unit-weight of organic matter relationship compared with the individual regression lines for 5 communities at Station IV . . . . . . 63 XV. Levels of production from July 19, 1958 to February 8, 1959 expressed in phytopigment units per 1.4 square decimeters per day . 67 XVI. Mean accumulative amounts of organic matter per 1.4 square decimeters per day per sampling period and gram—calories per square centimeter per day per sampling period plotted against time . . . . . 76 INTRODUCTION The measurement of productivity is a fundamental interest of the science of limnology. Primary produc- tivity of an ecological system, community, or any part thereof, is defined by Odum (1953) as the rate at which energy is stored by photosynthetic or chemosynthetic activity of producer organisms in the form of organic substances which can be used as food materials. Secondary productivity, the rate of energy storage at consumer trophic levels, is dependent upon primary productivity. The key word in the above definition is "rate"; the amount of energy fixed in a given time. The ideal way to measure productivity would be to measure the energy flow through the system, but this has so far proved difficult to do. Most measurements are based on some indirect quantity, such as the amount of substance produced, the amount of material used or the amount of by-product released. Odum (1956) has studied primary productivity in flowing waters in the large artesian springs in Florida by using diurnal gas curves and the upstream downstream methods of measuring community metabolism. Unfortunately, the methods used in the above procedure are not workable in the warm-water streams in Michigan because of the effects of organic pollution, the rapid change in water temperature, and the variability in volume flow. The large calcareous artesian springs have environmental conditions that are similar to a controlled laboratory experiment, the temper- ature and the volume flow are uniform throughout the year. The first mention of a specific technique for the study of aquatic organisms by means of introducing foreign solid substances was found in a Swedish publication (Naumann, as quoted by Cooke 1956). Since that time many "foreign solid substances" have been used to collect aquatic organ- isms. Microscope slides, glass plates, stones, cedar shingles, cinder bricks, and plexiglass plates are a few artificial substrates that have been used to study the complex of organisms that have become attached to the sub- strate. Plexiglass plates were used in this experiment because they are durable and are chemically inert. Considerable terminology has arisen in the literature describing communities of organisms which become attached to artificial or naturally occurring substrates. A history of the terminology and techniques of measuring this com- munity complex has been presented by Newcombe (1950) and Cooke (1956). The term aufwuchs as used by Ruttner (1953) will be used in this paper to describe the community of organisms that are firmly attached to a substrate but do not penetrate into it (in contrast to plants rooted in the bottom or certain parasites). When using artificial substrates for measuring organic production two assumptions must be made; (1) the substrates are not selective for specific organisms, and (2) the production on the artificial substrates occurs at the same rate as on natural substrates in the environment. The technique of collecting aufwuchs from an artificial substrate is not a direct measurement of production. The procedure embodies the collection of the accumulated standing crop over a uniform period of time, which is then used as an index of productivity (Keup, 1958). The larger the standing crop for a given period of time the greater the rate of production. The procedure is similar to the limit concept in calculus. If the time a substrate is allowed to remain in the water is decreased from a week to an hour, the more precise the estimate of productivity would become. The study was organized so that the use of artificial substrates to estimate production could be closely examined. Three methods were used to ascertain primary production in the experiment: (1) the accumulation of the number of organisms in a given time; (2) the accumulation of the weight of organic matter in a given time; and (3) the accu— mulation of phytopigment in a given time. Numeralizations of the relationships between these methods were expressed by calculating correlations coefficients. Identifications of algal organisms were made to compare taxonomic differences between sampling stations and to study community periodicity. However, the major consideration of the taxonomic work was to see the effects of community changes on the phytopigment unit-number of organisms relationship and the phytopigment unit-weight of organic matter relationship. Regression equations were utilized to compare the individual communities with the common regression line for each sampling site. A previous study has shown that nutrients are in abundance in the watershed (Brehmer, 1958). An attempt was made to correlate the photosynthetic rate with the rate of solar input. No known studies have been made in the lotic environment to establish the relationship between the photosynthetic rate and the rate of solar input. DESCRIPTION OF THE STUDY AREA The Red Cedar River is a typical southern Michigan warm-water stream. The upper portions of the watershed have been dredged to straighten and deepen the channels. The major tributaries have been dredged for agricultural purposes. Three artificial impoundments are found on the Red Cedar River. Treated and untreated sewage entered the river throughout its watershed. The souce of the Red Cedar River is Cedar Lake which is located in southwestern Livingston County in Sections 28 and 29, Township 1 North, Range 3 East of the Michigan Meridian. The river flows generally northwestward through Livingston County for approximately 18 miles and then west- ward through Ingham County for 28 miles, entering the Grand River within the city of Lansing (Fig. I). The period of minimum flow usually occurs in the fall of the year and the flow is highest during the late spring. A combination of unthawed ground, melting snow, and heavy rains occasionally brings about serious floods during the late spring. Meehan (1958) has summarized the climate, geology, soils, and land use of the entire watershed. Three sampling stations were established in the mainstream and one in Deer Creek, a tributary of the river. All four sampling stations were within a half mile radius Figure I. Drainage area of the Red Cedar River and its tributaries. LAKE LANSING Em M F0 LERVILLE V .J > T m a m is .80 _3 $10“ > 'E 'Hoaw o S E z ’I ga"-a° '80 m o 0" ° ~ 2 III ¥ ‘b a m 9 - £232.15 .2. '5 -= '~‘ j; 33%;. .‘d 1cHJ|w .99 3 O 'u “we? O 89 '41 '30 NINV1VN .80 '33 NVOO 3330 19 “V0 ‘5 CEDA‘ LAKE NMLES of Williamston, Michigan. The Williamston area was studied because rapid environmental changes occur within a rela- tively small area of the watershed. An artificial impound— ment is located in Williamston. A permanent and inter- mittent stream enters the river within the city limits. Sewage effluent is being added to the river from the city's sewage treatment plant. The station sites are shown in Figure II. Station I was established in Deer Creek 100 yards downstream from the bridge crossing Linn Road. The width of the tributary in the area sampled is approximately 8 feet, and the stream bottom material is sand. Deer Creek has been dredged and a levee has been built on both sides of the stream from the dredging. Station III, located in Section 35, Township 4 North, Range 2 East of the Michigan Meridian, was approximately 0.3 mile below the Williamston dam. Brehmer (1956) reports that this sampling area was downstream from six sewer out— falls which delivered a total estimated flow of raw sewage and septic tank effluent of 100 gallons per minute. Since the completion of the sewage plant in 1957, no raw sewage enters the river in this area. The river is approximately 50 feet in width with the bottom material composed of gravel and small rocks. Upstream from the sampling site are dense beds of Vallesneria americanna. The area is shaded by trees from late spring to early autumn. Figure II. Red Cedar River and sampling stations in the vicinity of Williamston, Michigan. H o m.:_2_lu.20m :05: i ..... H .. ............. / H ..... B u 11 Station IV was located in Section 35, approximately 0.6 mile below the Williamston Dam and below the confluence with Deer Creek. The area sampled is located immediately upstream from the sewage disposal plant. The river is approximately 40 feet in width with the bottom material composed of fine gravel and small rocks and is shaded similarly to station III. Station V was downstream approximately 1.0 mile from the Williamston Dam and 0.4 mile from the sewage treatment plant outfall. The width of the stream at this area is 40 feet and the bottom material is composed of silt and decomposed organic matter. The north river bank and its adjacent land is open pasture while the south bank had dense tree cover. There was no evidence of Spaerotilus, the sewage bacterium, often associated with polluted waters. METHODS AND TECHNIQUES In limnological and oceanographic studies there are many methods for measuring the productivity of a given environment. These may be summarized in two general cate- gories; one measuring photosynthetic rate and the other by obtaining quantitative estimations of plant material growth in a given period of time. Photosynthetic rate may be determined by the oxygen production in light and dark bottles or by the addition of a radioactive isotope as c14 to the medium and its subsequent estimation when fixed in cells after exposure. Quantitative estimation of plant material growth can be determined in several ways. These include measure of total weight; of constituents characteristic of plant' material that can be separated (e.g., chlorophyll) or estimated in mixtures (e.g., carbon, phosphorus; protein); of associated optical properties; and estimates from the counting of morphological units. Artificial substrates may be used as a sampling device. Cooke (1956) reviews the literature of fresh water community types and describes the concept of the aufwuchs community. He points out that aufwuchs are those organisms which are firmly attached to a substratum but do not pene- trate into it. Aufwuchs comprise all attached organisms, 13 except macrophytes, including both sessile and benthic organisms. The term "sessile" is also applied to organisms which become attached to artificially exposed material used for study of organisms. Therefore, any community of sessile organisms, plant orzmmhnal,established on an artificial substrate is an aufwuch community. The artificial substrates were plexiglass plates which were attached by screws to a wooden rack (Fig. III). The rack was attached to an aluminum bar which was driven permanently into the river bed. The dimensions of the shingles were 5" x 2" x 1/4” and whose area was 1.4 square decimeters. The substrates were collected in 6--9 days in the summer, lO--14 days in the autumn, and l4-—2l days in the winter period. The plexiglass substrates were collected after the aufwuchs growth was plainly visible but before a dense mat had formed. The substrates were removed from the stream, put in individual polyethylene bags, and stored temporarily in a portable ice chest. In the laboratory they were stored in a freezer until the organisms were removed from the plexiglass plates. It was found that freezing the attached organisms facilitated their removal from the substrates. Eight plexiglass plates were placed at a sampling site; four plates were used to determine the density of chlorophyll color and the remaining four used to determine the number of 14 Figure III. Plexiglass artificial substrates showing position, method of attach- ment, and actual size of substrate. «.GH , o¢®H MQH MGH NGH . . NGH «SH «SH l6 organisms per unit area. At Station IV both the weight of organic matter and chlorophyll were determined from each of four plexiglass plates. The remaining four substrates were also used to estimate the number of organisms per unit area. During a sampling period comparisons could be made between the relationship of numbers and chlorophyll color from each of four pairs of substrates. At Station IV, com- parisons were made not only of numbers and density of chlorophyll color but also between weight of organic matter and chlorophyll color. Counts of Cells The artificial substrates with algal organisms were thoroughly cleaned by rinsing and brushing the organisms into a 250 ml beaker. The organisms were transferred into a volumetric flask and mixed mechanically by using a Mag Mix. A volumetric pipette was used to draw off an aliquot from the volumetric flask and the subsample was placed in a Millipore Filter which had been partially filled with water. The size of the subsample was determined by the apparent density of the total sample. The water was drawn through the filter pad by vacuum, depositing the residue on the filter pad. The filter pad was removed from the apparatus, allowed to dry, and placed on a 3” by 1.5" glass slide. After the filter pad was thoroughly dried, one or two drops of immersion oil was placed over the residue and the filter l7 pad immediately became transparent, adhering to the glass slide. The slides were labeled and stored in slide boxes until counts and identification of organisms could be made. The Millipore Filter disc type HA used in this experi- ment has a pore diameter of 0.45 i 0.02 microns. These pores are distributed randomly over the entire surface and it has been estimated that the structural material makes up only 20 percent of the filter by volume, the remaining 80 percent being voids (Millipore Filter Corporation, 1957). The filters have a total depth of 150 microns. An important structural feature is that the pore diameter is small on one side of the membrane and much wider on the other side; that is, the pores are cone-shaped. The flow is always made to enter at the side of the narrow pore opening. The micro- scopic and submicroscopic particles are retained upon the filter surface or virtually in a single plane defined by the surface. The small pore diameter allows the filter pad to collect all algal organisms greater than 45 microns. The diatoms deposited on the filter pads can usually be identified to genus and often identified to species. Apparently, the immersion oil seeps into the striae of the frustrule and pushes out the chloroplast. Counts of the number of organisms were tabulated directly from the pads. The relative frequency of occurrence, the number of times an abundant organism was seen in 33 fields, Was also tab- ulated from the filter pads. If an organism was seen in 18 20 of 30 fields, the relative frequency of occurrence was 67 percent. To verify that the organisms were distributed ran- domly, the following test, which was developed by McGinnis (1934), was made. The formula for his index is as follows: Deviation from randomness (K) = D/d where D is the actual density or average number of organ- isms per field as determined by counting and (d) is the theoretical density. The theoretical density is tabled in McGinnis (op. git.) and is a function of the numbers of fields counted. A (K) value of 1 indicates randomness. Values in the neighborhood of 0.5 or lower indicate that the individuals encountered are more dispersed than would be by chance alone. Values in the neighborhood of 2 or more indicate that the individuals are more aggregated than would be expected by chance (Table I). The total number of organisms deposited on each filter pad can be calculated by the following formula: m = NX where m is an estimate of M, the total number of individuals on the area; N the total number of quadrats comprising the entire area; and X is the mean number of individuals per quadrat for a sample of n quadrats randomly chosen from N. TABLE I THE DISTRIBUTION OF AN AUFWUCHS SUBSAMPLE ON A MEMBRANE FILTER SHOWING A TEST OF RANDOMNESS* l9 Species F D d K=D/d Cocconeis placentula 90.0 2.21 2.30 0.96 Navicula cryptocephala 76.7 1.58 1.46 1.08 Gomphonema olivaceum 43.3 0.58 0.57 1.01 Cyclotella menehiniana 23.3 0.25 0.26 0.96 Cymbella spp. 16.7 0.18 0.18 1.00 Synedra ulna 10.0 0.10 0.10 1.00 Melosira virians 3.3 0.03 0.03 1.00 *Sample taken from Station I on 7/26/58 from 1.0 aliquot. Organisms scored at 1455 X (oil immersion). F = relative frequency of occurrence; D ..- - average number of organisms per field; d = theoretical density; K 2 test for randomness. 20 Identification of Organisms As was mentioned previously, qualitative identifi- cation can be made directly from the Millipore filter pads. However, the material remaining from the qualitative sub- samples was divided equally and stored in two types of algal preservatives; 6-3—1 preservative and concentrated hydrochloric acid. The concentrated acid was used to clean the frustrules of the diatoms and the 673-1 solution was used to preserve other types of algae which may have been seeded on the substrates. Organisms which could not be identified positively from the filter pads were identified from water mounts. Verification of previous identifications were also made from water mounts. A compound microscope with 10X and 20X objectives was used and all identifications were made under the oil immersion lens. Chlorophyll Color Two similar methods were utilized to obtain the density of chlorophyll color data. In the first method the periphyton growth was scraped from the substrates with a "rubber policeman" and allowed to stand in 95 per- cent ethanol for a minimum of 48 hours while stored in total darkness. Grzenda and Brehmer (ms.) indicate that samples can be stored in this manner for as long as 30 days with- <3ut a loss of the phytopigments due to decomposition. After the samples were filtered through glass wool, the Volume of the filtrate was adjusted to 50 ml by either 21 dilution or evaporation. The density of the chlorophyll solution was read on a Klett-Summerson colorimeter using the red filter (640—-700 mu). In the second method, the procedure was identical except that gooch crucible filtration was used. This technique was utilized in order that both organic matter and chlorophyll color could be obtained from the same substrate. Experiments by Grzenda and Brehmer (op. git.) dealing with opticochemical characteristics of 95 percent ethanol phytopigment extracts showed that the absorbancy of broad spectrum light (640--700 mu) is not linearly related to the concentration except at very low concen- trations. They point out that the measured pigment absor- bancy may be corrected to correspond with the theoretical absorbancy as related to concentration by constructing a correction graph (Fig. IV). The graph is constructed by plotting absorbancy against concentration as determined by dilution and this portion of the curve corresponds to the line labeled EXPERIMENTAL in Figure IV. The line labeled LAMBERT—BEER corresponds to the theoretical absorbancy of the solution. The correction graph is used in the following manner. The measured absorbancy is found on the ordinate and is followed horizontally to intercept the experimentally determined line. This intercept is then read vertically 22 Figure IV. Correction graph for adjusting measured phytopigment absorbancy values to units related to con- centration. ABSORBANCY 50 I0 I I I TTTIF I 11111441 I ILIILJI IO RELATIVE CONCENTRATION IOO 24 to intercept the extrapolated Lambert-Beer line. The absorbancy unit on the ordinate opposite this intercept represents the corrected absorbancy reading. Organic Matter All macro-faunal components of the aufwuchs com- munity were removed from the substrate and weight estimates of the components were made by the following procedure. After the periphyton was removed from the substrate and stored in 95 percent ethanol for at least 48 hours in total darkness, the particulate matter was separated from the solvent by filtration through a gooch crucible. The crucible was dried to constant weight and the organic weight determined by loss on ignition. The absorbancy of the ethanol-soluble pigments was determined after the solution was adjusted to a volume of 50 ml. The weight of the residue was added to the weight of the parciulate matter of the sample; the sum being an estimate of the total organic weight. The gooch crucibles and evaporating dishes at each step in the procedure were stored in a drying oven at 550 C and cooled to room temperature in a dessicator before they were weighed on an analytical balance. The sample was said to be at constant weight when two consecutive readins of i 0.5 mg were obtained after an interval of 12 hours. A flow chart for each step in the procedure is shown in Figure V. Comparisons were made between weight 25 Figure V. Flow chart showing procedure for obtaining estimates of organic matter from organisms attached to the substrates. GRZENDA TECHNIQUE SAMPLE «I- 95% ETHYL ALCOHOL PIGMENT I GOOOH FILTER / \ EXTRACT RESIDUE 0N FILTER I I COLORIMETER WEIGH I I EVAPORATE IGNITE- WEIG H WEIGH CRUGIBLE I I IGNITE-WEIGH TOTAL LOSS . \ / mes. LOST ON IGNITION FROM CRUCIBLE a FILTER 27 of organic matter and phytopigment units by calculating a correlation coefficient to express the relationship. Linear Regression and Correlation A linear regression was fitted to the phytopigment unit-weight relationship by the formula given in Walker and Lev (1953). The relation between Y1 (weight) and X1 (phytopigment unit) is called the regression equation and, for linear regression, is given by the formula 351:? + b (x yx ' X) i In this formula Y'is an estimate of the unknown weight from a known phytopigment unit (Xi)‘ X is the calculated sample mean of the phytopigment units and Y is the calcu- lated sample mean of the weight of organic matter. An estimate of the slope or the linear regression coefficient, b is calculated by the following formula: xy’ bxy = N233; ‘ QXIEIiY) Nix .. (2x) where N is the sample size; X is a known phytopigment unit, and Y is a corresponding weight for a given phytopigment unit. The correlation coefficient, r, is a numeralization of the observed phytopigment unit and the weight of organic matter. Correlation coefficients vary between +1 and -1 according to the closeness of the relationship in the 28 population sampled. A correlation of :.91 would indicate a close relationship while a coefficient of i-25 would indicate a poor relationship. A positive value for a correlation coefficient would show a direct relationship and a negative value would show an inverse relationship. The linear correlation coefficient may be calculated by the following formula: N330! - ($0421) [Nix2 - (1x )3] IX2Y2- (2302] where N is the sample size; X is a known phytopigment unit, and y is a corresponding weight for a given phytopigment unit. Linear regression equations and correlation coef- ficients were also developed for the phytopigment unit— number of organisms relationship using the same procedure. Water Temperature Water temperatures recorded for individual stations were taken with a pocket thermometer held approximately three inches under the water surface. The temperatures reported in Appendix A were recorded on a Taylor recording thermometer permanently located ten miles upstream from the mount of the river and ten miles downstream from Williamston. At most there was 0.50 C. difference between water temperatures recorded with the pocket thermometer and those with the recording themometer. 29 Solar Radiation Solar radiation data were obtained from the Michigan Hydrologic Research Station which maintains an Eppley pyrheliometer on the Michigan State campus. The pyrhelio- meter is located approximately 10 miles west of the area studied in the vicinity of Williamston, Michigan. Pyrhelio- metric stations measure "insolation," the rate at which solar energy is received on a horizontal surface at the surface of the earth. The unit of measure used in pyrheliometry, the gram- calorie, may be defined as the quantity of heat necessary to change the temperature of one gram of water from 3.50 c. to 4.50 D. (Crabb, 1950). The intensity of radia- tion is defined as the radiant energy emitted in a specific direction per unit area of surface per solid angle, hence, gram-calories per square centimeter. The average amount of light intensity was calculated for each sample period and is shown in Table 14. RESULTS AND CONCLUSIONS Qualitative Trophodynamic ecology cannot be separated naturally from community ecology; they are complimentary. Produc- tivity rates will vary not only between unlike communities during different seasons but also between like communities in the same season. The concept of the aufwuchs community was useful in delimiting the major producer complex responsible for primary production in the area studied. Many ecological studies have been made of the phyto- plankton of the lotic environment. Kofoid (1903, 1910) made complete studies of the plankton in the Illinois River, and Eddy (1932) studied the Sangamon River phyto- plankton in Illinois. The plankton of the San Joaquin River, California was investigated by Allen (1920). The upper Mississippi River's plankton was considered in a study by Reinhart (1931). Other workers who investigated phytoplankton in rivers and streams in the United States were Shelford and Eddy (1929), Brinley (1942), Lackey (1942, 1943), and Hooper (1947). Butcher's series of papers (1932, 1940, 1946, 1947) on studies of the ecology of rivers in Great Britain have led investigators to describe a new community type of algal organisms other than phytoplankton which are found 31 in great abundance in flowing water. This is the aufwuchs community, that group of organisms which are attached to a substrate but do not penetrate into it. Unfortunately, considerable terminology has arisen in the literature describing this community association. Sessile, benthic, epiphytic, periphyton are a few of the terms used but are synonymous with aufwuchs. Workers who have described an aufwuchs community in studies of flowing water include Blum (1954, 1957), Douglass (1958), Gumtow (1955), Odum (1957), and Whitford (1956). A community of aufwuchs was sampled in the Red Cedar using artifical substrates. Butcher (1932) reports that no observed differences in sessile algae were found on the artificial substrates (glass slides) than found on natural substrates in the river. 0n alternate sampling periods organisms were scraped from natural substrates in the river and compared with organisms from the artificial substrates. The artificial substrates were not selective, but had the same dominant organisms attached as did rocks, wood, and other naturally occurring substrates. The importance of diatoms as primary producers in the lotic environment cannot be overestimated. Reinhart (1931) points out that diatoms were at all times the most important constituents of the plankton in the Miss- issippi River from a volumetric viewpoint. The aufwuchs communities in the area sampled in the Red Cedar River I||.III|I' III ‘II III 32 are composed almost entirely of diatoms. Patrick (1952) states that the bottom microflora in the Des Moines River was composed almost wholly of diatoms and this undoubtedly is an important constituent of phytoplankton. Butcher (1932) states that diatoms comprise the largest and most prevalent group of algae in a river. He lists three dis- tinct sessile diatom communities: (1) a Diatoma- Gomphomema olivaceum community; (2) a Navicula viridula- Cymbella ventricosa community; and (3) a Synedra ulna community. In the Saline River, Michigan, Blum (1954) describes two winter diatom communities; (1) a Diatoma community, and (2) a Gomphonema community. Seven diatom communities were found in the aufwuchs complex in the Red Cedar River near Williamston; a Navicula cryptocephala community, a Cocconeis placentula community, a Gomphonema olivaceum community, a Diatoma hiemale com- munity, a Synedra ulna community, a Cymbella tumida com- munity, and a Cyclotella meneghiniana community. Some of these communities were short-lived while others persisted for relatively long periods (Table 2). Community periodicity refers to cyclic changes in the activities of organisms which produce regularly recurring changes in the complexion of the community as a whole. Ecologists studying terrestrial and fresh water communities in temperate regions have found that early and late spring or early and late summer are as different 33 TABLE 2 A LIST OF DOMINANT ORGANISMS AT EACH STATION ON DATES OF OCCURRENCE Dominant Organism Dates of Occurrence Station I Cocconeis placentula 7/17/58 to 9/11/58 Navicula cryptocephala 7/17 58 to 8/18/58 Navicula cryptocephala 9/3 59 to 9/11/58 Cymbella tumida 9/11/58 to 9/21/ 58 Navicula cryptocephala 9/21/58 to 11/ /7/ g58 Diatoma hiemale 11/ /7/ /58 to /26 558 Synedra ulna 1//26/58 tol/ Navicula cryptocephala 6/59 to 2/ Station III Navicula cryptocephala 7/17/58 to 8/18/58 Cocconeis placentula 8/18/58 to 9/11/58 Navicula cryptocephala 9/21/58 to 9/30/59 Synedra-ulna 9/30 58 to 11/26/58 Diatoma hiemale 12/ /58 to 12/20 58 Synedra ulna 12/20/58 to 2/8 59 Station IV Navicula cryptocephala 7/19/58 to 8/26/58 Cocconeis placentula 7/19 58 to 9/30/58 Cyclotella meneghiniana 9/3 58 to 9/21/58 Navicula cryptocephala /11/58 to /28 558 Synedra ulna 1//28/58 tol/ Gomphonema olivaceum 6/58 to 2/ Station V Navicula cryptocephala 9/30/58 to 11/7/58 Synedra ulna l//2//58 to 1 25/59 Gomphonema olivaceum 25 9 to 2 8/59 34 from each other as autumn and winter. Odum (1953) sug- gests that the factors responsible for periodicity may be: (1) extrinsic-—entirely dependent on an external environ- mental stimulus; (2) intrinsic-~synchronized with an environmental stimulus but capable of persisting in its absence; and (3) inherent-~independent of environmental changes. Transeau (1913), Pearsall (1932), and Hutchinson (1944) describe fresh water periodicity in lakes and attempt to correlate factors responsible for algal per- iodicity. However, there is some doubt whether or not periodicity occurs in the flowing water environment. Butcher (1940, 1947) points out there is no seasonal variation in dominant species in the Hull and Itchen Rivers in Great Britain. He has found seasonal periodicity in the Lark and Tees Rivers (1932). Gumtow (1955) reports periodicity in the West Gallatin River, Montana and Blum (1957) has found definite cyclic changes in the algal communities of the Saline River, Michigan. Data from the Red Cedar River show a marked seasonal periodicity of algal organisms which become attached to artificial substrates (Figs. VI and VII). Navicula cryptocephala. This tiny diatom was found in great abundance at all sampling stations from the beginning of the sampling in July and persisted until late November. However, at Station I it began to reappear in 35 FIGURE VI. Seasonal periodicity of algal organisms which become attached to artificial substrates at Station I ZS. own >02 . POO Faun 03¢ . .53 ”I + m _ ml . a . . . .o. W 3 V .8 N m .on m :9. R w 8 O .00 M ..A .2. m M I II r05 0 m .. .8 U o. 3 . .3 W 3 .oo. m0 4.50.: 32.53.... Quzooooo u...<:u.: 420.25 42.5 5.3sz H 20.._.<._.m 37 FIGURE VII. Seasonal periodicity of algal organisms which became attached to artificial substrates at Station III. up C l""“. 23u0<>30 (Smart-.00 x x xxx xx ¢0 (4:0;(2 ll! (Jzkzm0<4a 03200000 (2...: (cows->0 II I II I H 20:45.0 in .5... .00. BONBHNDOOO :IO AONSIIOSUJ NVSN 39 FIGURE VIII. Seasonal periodicity of algal organisms which became attached to artificial substrates at Station IV r 24... . own— >02 P00 Plum 03< .55 a “a 0. n a X x '08 X x '8 X x .2. X X v. :00 X x .3 n X [0.2. x. / x // .00 a /, X I. '8 :00. (252.10%, SJWPOJOPO ooOoOOoooooaooo 4J¢0 (1:40:22 3381,30 (339g xxxxxxx X xx jakzuzu—m 05200000 ............. (2.5 (202m NH ZOFdFm H 83:1 1.1! BONSNUI'IOOO :IO AONHI'IOBNJ NVBW L11 FIGURE IX. Seasonal periodicity of algal organisms which became attached to artificial substrates at Station V 03¢ ..:...a T 23. . own 0 >02 . ._.00 _ _ a _ _ x c... x X x x x x X X x ./ x «x x u / x x x X x X m 23m0¢>30 (222021100 X xxxxxxx <4<1¢NO0P§¢0 4.50.32 42.5 <¢0u2>0 I I I I .H 20_._.<._.m 0. ON 0 Q' 0 D HINOW 33d BONBUHOOOO :IO AONBHOBHS NVBW O 00 #3 great numbers in January. There is no apparent means of attachment found in this diatom. Blum (1957) found 3. cryptocephala to occur dominantly throughout the summer in the Saline River. Gumtow (1955) mentions that Navicula was most abundant during August--September but became predominant again during early December and remained in this position through March. Cocconeis placentula. This diatom occurred with E. cryptocephala to form a Navicula cryptocephala--Cocconeis placentula community during the summer. It did not persist in abundance with E. cryptocephala and declined rapidly when the water temperature fell below 150 C. Butcher (1932) found this species as late as October but it never occurred abundantly during the winter. It is attached to the substratum by the whole of one surface. Synedra ulna. The largest diatom found in the auf- wuchs complex, this species first appeared in abundance in October. This winter species was capable of persisting in great numbers through January in low temperature (00 C.) and under cover. Butcher (1932) mentions that this species occurs most abundantly during the winter months but Blum (1957) lists this as an abundant form in the summer micro- flora of the Saline River, Michigan. This means of attach- ment to a substratum is by a mass of mucilage at one end of the frustule. Gomphonema olivaceum. Another winter species, this alga was beginning to reach abundance in January. The species was part of the winter diatom community in the Saline River and disappeared in mid-April with the general rise in water temperature (Blum, 1957). A massive colonial form, it has individual cells which attach to a substratum by branched or unbranched mucilaginous pedicels. These colonies are often macroscopically visible. Diatoma hiemale. Occurring at Stations I and II, its maximum abundance was during November and December and it did not persist under ice cover. It attaches to a substratum by a mass of mucilage at one end of the frustule. Cymbella tumida. This species was found only in Deer Creek, a tributary of the river. Each unit of vegetation is attached by the whole of one surface. It occurred abundantly for one week in September. Blum (1957) lists 9. tumida as occurring abundantly during the summer. Cyclotella menehiniana. The only centrate diatom occurring in the samples, this alga was abundant during the month of September at station IV. There is no visible means of attachment for this organism. Plates of the dominant forms and a few of the rare species are in Appendix B. 45 Quantitative Results Three methods are used to estimate primary production (1) the number of organisms per unit area per sampling period; (2) the weight of organic matter per unit area per sampling period; and (3) the amount of phytopigment unit per unit area per sampling period. The results from these methods are enumerated in Appendix D. Numeralizations of the relationships between these methods are expressed by correlation coefficients. The nature of period community changes at each station are considered by comparing the individual community regression lines with the common regression line for that station. Levels of production between stations are compared and the solar input rate- production rate relationship is considered. The relation between phytopigment units and the number of organisms. The coefficients of linear correla- tions calculated for the four stations were .90, .84, .75, and .86. These results are excellent for biological data and indicate a close relationship between the independent variable, the phytopigment unit, and the dependent variable, the number of organisms sampled. The probability of obtaining correlations as great as these through chance alone is less than .001 (Snedecor, 1957). Identification of the diatom communities in the water:shed near Williamston, Michigan have shown the SPeatest number of individual dominant communities occurring 46 in Deer Creek. The range of phytopigment units shows the widest fluctuation in Deer Creek compared with the other sampling sites (Appendix D). However, this station has the highest correlation coefficient calculated. A comparison of the individual correlation coeffi- cients indicate there may be differences between Deer Creek, the tributary of the main stream, and the sampling sites in the main stream (Table 3). TABLE 3 A COMPARISON OF THE REGRESSION COEFFICIENTS AND CORRELATION COEFFICIENTS EXPRESSING THE PHYTOPIGMENT UNIT-NUMBER OF ORGANISMS RELATIONSHIP FROM THE FOUR SAMPLING SITES Correlation Regression Station Coefficient Coefficient Intercept I .90 14.4 -.83 III .84 9.11 .53 IV .75 7.18 .24 V .86 7.89 .16 A test of the hypothesis that the individual cor- relation coefficients were from the same population shows a significant difference at the 5 percent level (Table 9). There is evidence the ratio of phytopigment units to number or organisms may be larger in Deer Creek than for the Stations in the mainstream (Figs. X--XIII). 47 TABLE 4 A STATISTICAL COMPARISON OF FOUR CORRELATION COEFFICIENTS TAKEN FROM THE PHYTOPIGMENT UNIT-NUMBER OF ORGANISMS RELATIONSHIP IN THE RED CEDAR WATERSHED* Station N N-3 r Zr ”(N-3)Zr (N-3)Zr2 Corgected r. I 79 76 .903 1.488 113.088 168.275 1.483 III 76 73 .837 1.211 88.403 107.056 1.205 IV 80 77 .750 .986 75.922 74.859 .981 V 44 41 .855 1.275 52.275 66.651 1.266 267 3 345 329.688 416.841 Average r 3.345/4 = .836 Average ZR 329.688/267 = 1.235 (N - 3)Zr Zr = 329.688 x 1.235 = 407.165 (N — 3)zr2 - (N - 3)Zr in = 416.841 - 407.165 = 9.626 2 x36”. = 9.626 Reject if 9.678 > 7.80 at 5% level. Reject if 8.076>ll.3 at 1% level. Therefore, reject at 5% level; accept at 1% level. 328.116 (N - 3) Corrected Zr 328.116/267 = 1.229 Average Corrected Zr Average r = .8417 *Test taken from Snedecor (1956) indicate: N = total number of samples r = linear correlation coefficient Zr = log transformation from r to a quantity 2 which has a normal distribution Corrected Zr = accounts for small bias in Zr when unequal samples are used 48 The high correlation coefficients may be a result of the type of organisms sampled. Tucker (1949) found a good correlation (.84) between number of units of phyto- plankton counted and density of pigment extracted. In population he studied, over 90 percent of the organisms sampled were diatoms. Lower correlations were found for heterogenous groups of phytoplankton algae. At least two major dominant community types developed at each station during the sampling period from July, 1958 through February, 1959. In a given sampling period, a maximum of 11 genera and approximately 20 species were enumerated from a subsample of a single substrate. The periodic change in community structure and the number of individual species found in a single subsample indicate variability. Yet, high correlations were found and the similarity between regression coefficients indicate that number of organisms may be estimated from phytopigment units by using artificial substrates. The good correlation might be attributed to the size of the organisms, all the diatoms sampled being relatively the same size except giynedra ulna. Since most organisms are approximately ishe same size, a given volume of chlorophyll would be extracted from each organism. An estimate of the total number Of organisms found (HI a substrate can be calculated from the following f0I‘mula: _ m = NXK 49 where m is the total number of organisms per 1.4 sq. dm.; N is the total number of fields (44,484) on the filter pad under the oil immersion lens; I the mean number of organisms per 30 fields; and K is 100, a multiplicative constant which considers the size of the subsample. A tentative hypothesis that the community structure might be grossly altered because of the addition of nutri- ents from the sewage disposal plant was rejected. No gross differences in community structure were observed between station V, the sampling site 0.4 mile below the sewage disposal plant, and the other sampling sites in the river. It should be noted that a sampling site was not established at this location until September 30, 1958 while Sites were established during July at the other stations. An increase in nutrients during the summer may change the level of productivity or alter the community structure. If phytopigment units were used to estimate the number of organisms on an artificial substrate throughout the entire year,the effect of periodic community changes should be considered. The results of an analysis of co- ‘variance between dominant communities at each station EShow that one regression line may be used to estimate runnber of organisms except at station III (Tables 5-m8). Tfiue sampling site in Deer Creek was the only station where 61 common slope could be used in estimating the number of Orwganisms. Individual community regression lines are 50 FIGURE X. The common regression line expressing the phytopigment unit-number of organisms relationship compared with the individual regression lines for 4 communities at Station I. STATION I \‘ J, o a} L'z' a) X V. 9: g. I _Ii I I I I .I I |\ _O>IQ db _ I I Imo.n+x no?» no...» 0. no. Hm. 29.55% HEIIVW OINVOHO 0W :IO 65 TABLE 9 A COVARIANCE ANALYSIS BETWEEN REGRESSION LINES FOR PHYTOPIGMENT UNITS AND WEIGHT OF ORGANISMS FOR 5 COMMUNITIES AT STATION IV _; f H Degrees of Sum of Mean Source of Variation Freedom Squares Square TOTAL 78 839.48 --- 1. Can one regression line be used for all observations? Gain from separate regression over general regression 4 349.66 87.4150 Deviation from separate regression 74 489.82 6.6192 ("F" a 13.206, answer is NO) 2. Can a common slope be used for the separate regression lines? Further gains from fitting separate regressions (difference between slopes) 4 41.23 10.3075 Deviations about separate regressions 70 448.59 6.4084 ("F" = 1.61, answer is Yes) 66 within groups from a line with a common slope. The low level of productivity occurring during the winter months would be significantly different from the common mean and the common line. This can be depicted graphically by five parallel lines with a common Slope but one Of these lines significantly lower than the other four lines. The lower line in this case represents the low level of winter production. The development of a reliable predictor equation for estimating the amount Of organic matter from the phy- topigment unit would be an excellent tool for estimating primary productivity. Any estimation of the amount of organic matter produced on a substrate envolves consid- erable laboratory time. The phytopigment unit can be obtained in a short period of time. However, the weight of organic matter can be converted into energy units and the efficiency Of primary producers can be estimated. The predictor equation calculated in this experiment for estimating the weight of organic matter of diatoms from the phytopigment unit can be used except during low levels of production. Variation in primary production. The aufwuchs pro- duction in the Red Cedar River near Williamston, Michigan demonstrated both seasonal variation and variation between individual stations (Fig. xv). Brehmer (1958) indicated that there was a decrease in production of organic material 67 Figure XV. Levels of production from July 19, 1958 to February 8, 1959 expressed in phytopigment units per 1.4 square decimeters per day. mmm. mmm_ . m Mn. .24.. due .>oz Foo kamw . end has 9 o. a .. m 8 8 N 2. 9. s s m 8 on M 2. 2. w on o. on H zo_._.<._.m W 3. I. e .m. In. um 8 Wm H ZO_._.<._.w mum w o. S on 0 on m 0.. H. zo_._.<._.m on G 3 o. 84:23 2: D 2 m on m... 9. H on H. 29.2.5 mm. 8 Foo ..Emm .o:< NS... 0 . w 69 through the fall period in 1957 and an absence Of the characteristic autumn maximum frequently recorded for a lentic environment. A general increase in phytopigment production was recorded for the autumn period in 1958. A sharp decrease in phytopigment production was evident as ice cover developed on the river system. During the winter period the ice cover reached a maximum thickness of 14 inches in Deer Creek and was frequently covered with 12 inches of snow. This excluded a large portion of the available light from the producer organisms and greatly reduced primary production. Using a randomized block experiment with 4 phyto- pigment units within a cell, a two-way analysis of variance was made to statistically determine variability in pro— duction. The results show that there is significant difference in means between stations, between dates, and the interaction between stations and dates (Table 10 and Table l2).‘ Duncan's Multiple Range Test (1955) was utilized to ascertain which station means were signifi- cantly different from one another and which were not The results in Tables 11 and 13 indicate that the pro- duction between sampling stations in the mainstream is not significantly different but Deer Creek shows signifi- cantly greater production than found at any station in the river. 70 TABLE 10 ANALYSIS OF VARIANCE OF THREE STATIONS IN THE RED CEDAR WATERSHED FROM JULY 19, 1958 TO SEPTEMBER 30, 1958 L ‘- -— L __ Source of Sum of Degrees of Mean Variation Squares Freedom Square "F" TOTAL 5,075,764 107 -- -- Cells 3,975,611 26 152,908.1 11.258 Dates 1,756,687.3 8 219,585.9 16.167 Stations 1,005,553.5 2 502,766.8 37.017 Dates x Stations l,2l3,390.2 l6 75,836.l 5.584 Residual (error) 1,100,153 81 13,582.1 —- 1. Are the means between dates equal? ("F" = 16.17, answer is No) 2. Are the means between stations equal? ("F" = 37.02, answer is No) 3. Are the means from the interaction between dates and stations equal? ("F" = 5.58, answer is No) 71 TABLE 11 DUNCAN'S MULTIPLE RANGE TEST SHOWING SIGNIFICANT DIFFERENCES BETWEEN STATION MEANS FROM JULY 19, 1958 TO SEPTEMBER 30, 1959 Standard Error of a Station Mean Sm =‘VResiduai/4 =‘V13,582.1/4 = V3,395.53 = 58.24 Station Means Ranked in Order IV III 109.2 135-9 Shortest Significant Ranges p: (2) 5% Table ' Values 2.86 Rp: 166.57 I I - IV = 325.9 - 109.2 I -III = 325.9 - 135.9 III - IV = 135.9 - 109.2 I 325.9 (3) 3.01 175.30 216.737175.3O Sig. dif. l90.0>166.57 Sig. dif. 26.7100.10 Sig. Dif. V - III = 148.20 - 113.73 = 34.97 £105.35 V - IV = 148.20 - 147.43 = 1.27¢100.10 IV - III 2 147.43 - 113.73 = 33.70 (100.10 74 The nutrient levels in the mainstream of the water- shed are in gross abundance compared to those found in the tributary according to Mr. Robin Vannote, a graduate student studying the nutrient levels in the Red Cedar River watershed. He also points out that there is a greater stability of physical and chemical conditions in the mainstream than found in the tributary. However, organic production was found to be greater in the tribu- tary even under seemingly adverse conditions. Solar radiation. The effect of light intensity, that amount of energy reaching the earth‘s surface, has not been studied for the lotic environment. It has been shown that the rate of photosynthesis in a lentic environ- ment is frequently lower at the surface than at 3 meters' depth (Nelson and Edmonson, 1955; Schomer and Juday, 1935; Manning and Juday, 1941). These observations are inter- pretable on the basis that the saturation intensity of light for photosynthesis by a number of algae is quite low relative to the intensity of full sunlight, and more- over actual inhibition due to photo-inactivation of the photosynethetic mechanism may take place in bright light. However, certain littoral algae species do not show inhibition at high light intensities (Manning, Juday, and Wolf, 1938; McMillan and verduin, 1935). Precise estimates of light intensity were not taken at each sampling site, but light data were Obtained from 75 a pyrheliometric station 10 miles from the sampling area. It seems that the photosynthetic rate is correlated with the energy input rate (Fig. XVI). Moreover, there is evidence that light intensity does not inhibit the auf- wuchs communities. The levels of production were signifi- cantly higher during the summer in Deer Creek which had no shade cover than the levels of production in the main- stream which had shade cover. When the foliage was com- pletely removed by the end of October the differences between all stations in the level of production were negligible (Fig. XV). Apparently the producers are pro- tected from the inhibitory effect of light intensity by the color and turbidity associated with warm-water streams. A characteristic fall pulse in the lotic environ- ment may be a result of two interacting factors (1) an increase in the energy input rate due to the removal of shade cover, and (2) an increase in the nutrient levels due to a decrease in the volume flow. However, if the water levels are raised sufficiently by rainfall during this period, a subsequent increase in turbidity and the dilution of the nutrient levels would eliminate the possibility for a fall maximum in production. The low levels of production in the winter can be attributed to ice cover which reduces the amount of energy available to the producer complex. Following the winter solstice which occurs about the 20th Of December, a gradual 76 Figure XVI. Mean accumulative amounts of organic matter per 1.4 square decimeters per day per sampling period and gram- calories per square centimeter per day per sampling period plotted against time. SBIHO‘IVO—WVHS BAIIV'IIIWIIOOV 24.. owo >02 #00 Pamm 009T 000 N, coon 000v. OOOn. 000m. mm._.._.