Determination of the Relative State of Eutrophy of Navigation Pool No

Home , Black River (Wisconsin), Lake Onalaska

DETERMINATION OF THE RELATIVE STATE OF EUTROPHY OF NAVIGATION POOL NO. 7 OF THE UPPER MISSISSIPPI RIVER BY MEANS OF AN ALGAL ASSAY PROCEDURE

A Thesis

Submitted to the Faculty of University of lrJisconsin La Crosse

Stephen M~ Clark

In Partial Fulfillment of the

Requirements for the Degree

Master of Science

July 1974 '4- ) ,. "V

UNIVERSITY OF WISCONSIN La Crosse, Wisconsin 54601

COLLEGE OF ARTS, LETTERS, AND SCIENCES

Candidate: Stephen M. Clark

We recommend acceptance of this thesis to the College of Arts, Letters, and Sciences in partial fulfillment of this candidate•s requirements for the degree Master of Science in Biology . The candidate has completed his oral defense of the thesis.

107/1 I I I '-1

This thesis is approved for the College of Arts, Letters, and Sciences ii

ABSTRACT

This study was undertaken to refine a method to determine the eutrophic state of water by the application of a static bioassay pro cedure with algae as the test organism. The procedure was applied to Navigation Pool No. 7 in the Upper Mississippi River (Dresbach, Minnesota) to determine the effect of this navigation pool on nutrient dynamics of the river.

Water samples were collected from four sampling sites twice per month from March 12 to October 1, 1972. The pH, temperature, nitrate

- 1 ) - 3 ) (N0 3 and phosphate (Po 4 were determined for each sample. Filtered water samples were inoculated with a predetermined quantity of Scenedesmus quadricauda and Chlorella vulgaris and a known amount of

14 • NaHC 03 Samples were incubated for 2 hours under controlled environ mental conditions. Incorporation of C14 during photosynthesis provided a direct approach to the measurement of primary productivity.

Productivity values (mgC/1) and nitrate - 1 ) and phosphate (No 3

- 3 ) (Po 4 levels were at a maximum in March and a minimum in May, June and August. Due to nutrient levels in excess of those required for maximum productivity, no significant correlations were detected between productivity values and the nitrate and phosphate levels observed. The upstream sampling site demonstrated significantly higher (0.1) produc tivity values, nitrate levels and phosphate levels than downstream iii sampling sites. Navigation Pool No. 7 appeared to be an effective nutrient trap. Incoming nutrients were assimilated into the abundant plant growth and subsequently trapped within the sediments. Decay of this vegetation appeared to be responsible, in part, for cyclic nutrient phenomena within the pool. iv

TABLE OF CONTENTS page LIST OF TABLES ...... v

LIST OF FIGURES...... Vi

INTRODUCTION ...... :. 1

METHODS AND r~ATERIALS. 7

Sampling ..... 7

Chemical measurements 8

Production of inocula 9

Preparation of inocula. 9

Preparation of test flasks. 10

Preparation of the sample for counting. 10

RESULTS AND DISCUSSION . 12 Results and discussion. 12 Conclusions ...... 19

SELECTED REFERENCES...... 21

APPENDIX ...... 24 v

LIST OF TABLES / Table Page 1. Primary productivity (mgC/1 /hr), nitrate (NO 3 1), and phosphate (P04-3) levels in Navigation Pool No. 7, recorded at Site I, Lock and Dam No. 7, Dresbach, Minnesota, 1972 ...... 24

- 1 2. Primary productivity (mgC/1/hr), nitrate (NO 3 ), and phosphate (PO; 3) levels in Navigation Pool No. 7, recorded at Site II, on French Island, La Crosse, Wisconsin, 1972 ...... •...... 25 3. Primary productivity (mgC/1/hr), nitrate (NOt 1), and phosphate (P04 .. 3) levels in Navigation Pool No. 7, recorded at Site III, the Onalaska Spillway, Onalaska, Wisconsin, 1972...... 26

4. Primary productivity (mgC/1/hr), nitrate (N0 3-1), and phosphate (P0 4-3) levels in Navigation Pool No. 7, recorded at Site IV, the Brice Prairie Boat Landing, Brice Prairie, Wisconsin, 1972...... 27 5. Correlation coefficients (r) bet\'Jeen productivity . of test species and nitrate (No3-1) 1eve 1s in Navigation Pool No. 7, 1972...... 28 6. Correlation coefficients (r) between productivity of test species and phosphate (P0 -3) levels in 4 Navigation Pool No. 7, 1972...... 28 . 7. Test of significance between productivity values of selected pairs of sample sites in Navigation Pool No. 7, 1972...... •..... 29

8. Test of significance between nitrate (N03- 1 ) values observed at Brice Prairie Public Boat Landing and several sites in Navigation Pool No. 7, 1972. 30 9. Test of significance between phosphate (P04- 3) values observed at Brice Prairie Public Boat Landing and several sites in Navigation Pool No. 7, 1972. 30 vi

LIST OF FIGURES / Figure Page 1. Location of sampling sites in Navigation Pool No.7, 1972 ...... 31 2. Primary productivity (mgC/1/hr) for Scenedesmus guadricauda and Chlorella vulgaris at Site I in Navigation Pool No. 7 at Lock and Dam No. 7, Dresbach, Minnesota, 1972 ...... 32 3. Primary productivity (mgC/1/hr) for Scenedesmus guadricauda and Chlorella vulgaris at Site II in Navigation Pool No. 7 at French Island, La Crosse, Wisconsin, 1972...... 33 4. Primary productivity (mgC/1/hr) for Scenedesmus guadricauda and Chlorella vulgaris at Site III in Navigation Pool No. 7 at the Onalaska Spillway, Onalaska, Wisconsin, 1972 ...... 34 5. Primary productivity {mgC/1/hr) for Scenedesmus guadricauda and Chlorella vulgaris at Site IV in Navigation Pool No. 7 at the Public Boat Landing, Brice Prairie, Wisconsin, 1972...... 35

1 6. Nitrate (No 3 - ) and phosphate (Po 4 -3) levels (mg/1) at Site I in Navigation Pool No. 7 at Lock and Dam "No. 7, Dresbach, Minnesota, 1972...... 36

- 1 ) - 3 ) 7. Nitrate (No 3 and phosphate (Po 4 levels (mg/l) at Site II in ~avigation Pool No. 7 at French Island, La Crosse, Wisconsin, 1972...... · · . · . · 37

8. Nitrate (No - 1 ) and phosphate (Po -3) levels (mg/1) 3 4 at Site III in Navigation Pool No. 7 at the Onalaska Spillway, Onalaska, Wisconsin, 1972 ...... 38

1 3 9. Nitrate (N0 3- ) and phosphate (P0 4 - ) levels (mg/1) at Site IV in Navigation Pool No. 7 at the Public Boat Landing, Brice Prairie, Wisconsin, 1972. 39 INTRODUCTION

In the past few decades, human cultural activities have accelerated the natural rate of eutrophication and lead to disturbances of freshwater ecosystems. The term 'eutrophication' adopted by the Eutrophication Group of the Organization for Economic Cooperation and Development is defined as: 11 the nutrient enrichment of waters, which frequently results in an array of symptomatic changes, among which increased production of algae and other aquatic plants, deterioration of fisheries, deteriora tion of water quality, and other responses are found objectionable and impair water-use 11 (Bartsch, 1970). Eutrophication due to mans' activities is as old as history and regardless of the point on the time scale that human influence is added, the end result is the same: the aquatic environment moves more rapidly to advanced stages of eutrophica tion (Hasler, 1947).

Only recently have people noticed and demanded workable solutions to the problem of accelerated eutrophication. One approach to this problem is to study the effects of eutrophication on the primary producer organisms present in a given body of water. The rate of carbon fixation at the primary producer level provides an assessment of the interaction of physical, chemical, and biological factors which determine the actual fertility of any environment (Goldman, 1961). The level of fertility and the rate of primary production are of fundamental importance for the understanding and comparing lakes as biological units (Goldman, 1960).

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Productivity is a major factor to consider in classifying lakes since changes or differences in basic productivity influence the rate

of accumulation of organic matter in successive trophic levels~ Ryther (1956) stated that the productivity of natural waters is judged on the quantity of organic matter which they support at a given moment, but he emphasized that production must be considered as a rate. MacFayden (1948) defined productivity as equal to the rate of flow of matter. Lindeman

(1942), in proposing the trophic-dynamic view of ecology, re~ognized the importance of rate measures and the need to develop means of better quantifying rate functions. The interest in energy transformations helped to establish rates as being a more meaningful measurement than standing crop (Goldman, 1961). In examining an ecosystem, one is primarily concerned with the real production of organic matter that is added to the environment, or net photosynthesis. Primary productivity is thus taken to be the net rate of fixation of organic carbon in photosynthesis (Goldman, 1960).

There are dangers inhe~ent in predicting productivity with chemical measurements alone.· The mere presence of chemicals does not prove their biological availability (Hutchinson, 1944; Potash, 1956). There is - considerable variation in nutrient levels from week to week. Qualitative effects of phytoplankton periodicity are most likely due to these fluctua tions in nutrient levels. Clear-cut correlations between chemical conditions and productivity are not to be expected. Among the several factors one must consider in any productivity study are (1) inorganic nutrients other than nitrogen and phosphorus, (2) presence of organic substances in the water, (3) the physiological conditions of the organisms tested and (4) competitive relationships between test organisms -3-

(Hutchinson, 1944). Productivity is most frequently defined on a chemical basis by examining nitrogen and phosphorus levels. Hasler (1947), Verduin (1956), Hutchinson (1957) and Potash (1956) all stated that nutrients other than nitrogen and phosphorus are normally present in excess. Although nitrogen and phosphorus are often found to be limiting in natural environments, their presence is not necessarily directly proportional to the general state of eutrophy. One must consider the levels of all requirements for plant growth. 1his implies that a biological assay method be employed along with chemical measure ments to determine the relative state of eutrophy of a given body of water.

The use of an algal assay procedure for examination of the eutrophic state of a body of water has the following advantages: {1) the inclusion of all dissolved substances in the assay procedure, and (2) comparability of data from several sites in the same environmental system. Pure culture bioassay techniques present problems when one attempts to apply the data to the natural environment. Algae grown under standard conditions of light and temperature act differently than in the natural environment where these factors are highly variable. Development of a standard method to assay the actual ability of water to support primary production necessitates elimination of such variations by assumption. The procedures and principles employed by the author to determine the ability of various aliquots of water in the Upper Mississippi River to grow algae were a modification of those developed by the Joint Industry/ Government Task Force on Eutrophication (Bueltman, 1969).

The purposes of this project were to (1) refine a method by which -4- the eutrophic state of water could be determined by applying a static bioassay procedure with algae as the test organism, (2) to apply this procedure to water of Navigation Pool No. 7 in the Upper Mississippi River in the vicinity of La Crosse, Wisconsin, and (3) to determine what effect the presence of navigation pools has on the nutrient levels of the river.

Methods of measuring primary productivity have been available since .. the 1920's, but a major advancement came with the use of the sensitive C14 technique (Steeman Nielsen, 1951, 1952). Basically, the technique involves introducing a known amount of C14 as bicarbonate into an aliquot of water containing phytoplankton. The phytoplankton incorporates some 14 of the C during photosynthesis. The assimilation of C0 2 provides the most direct approach to the measurement of primary productivity, for the uptake of C0 2 is equivalent to the production of organic carbon. The amount of C0 2 assimilated may be measured by filtering the algal cells and counting their activity. Such a technique is valuable in that the carbon content of the water is not increased significantly and its sensitivity permits.measurements where the photosynthetic rate is as low as 0.02 ~g C/l (Ryther, 1956). Use of this method assumes that: Activity of Phytoplankton (k) = Total carbon assimilated Activity of C14 added Total carbon available The constant (k) corrects for the isotope effect. C14 is assimilated at a rate six per cent less than C12 due to mass differences. The total availability of carbon is essential for calculation of photosynthetic rates in C14 experiments and is based on total alkalinity (Hutchinson, 1957). The equation for photosynthesis does not describe the complex processes of growth, for products are converted into proteins, fats, etc. -5- as well as carbohydrates. Primary productivity becomes more analogous to growth than photosynthesis, but such relationships cannot be expressed with simple equations {Ketchum and Redfield, 1949).

The method outlined above was applied to waters of Pool No. 7 in the Upper Mississippi River. Pool 7 is one of a series of pools formed by impoundment of water behind locks and dams designed to provide a minimum depth of nine feet for navigation from the mouth of the Missouri River to Minneapolis. Lock and Dam No. 7, forming the downstream end of Navigation Pool No. 7, is located 1130 km above the mouth of the Ohio

River and 7. 4 km above the city of La Crosse, t~li scans in (Fig. 1 ) . The pool extends for 19 km to Lock and Dam No. 6 located at Trempealeau, Wisconsin. The water area of the pool is 5440 ha with a primary shore line of 60 km (U. S. Army Corps of Engineers, 1968).

The topography surrounding Pool No. 7 on both the Wisconsin and Minnesota sides of the Mississippi River is characterized by high bluffs and steep valleys. This region, known as the DriftlessArea! shows no signs of glacial activity,-although the lowlands and floodplain areas consist of alluvial' terraces deposited by glacial stream outwash. Prior to the construction of the locks and dams in the 1930's, the river bottoms were primarily wooded islands separated by deep sloughs and numerous small lakes and ponds. Inundation altered the conditions and created pools which exhibit three distinct zones. The upper end of each pool remains essentially like the original river where the water levels are not raised to any extent and the old conditions of deep sloughs and wooded islands are found. In the middle of each pool, water backs up over the islands, spreading out and forming large areas of comparatively -6-

shallow water. In the lower end of the pool and immediately above each _dam, an open lake-like aspect is found (Fremling, 1973). The impounded waters at the lower end of Pool No. 7 form an extensive body of shallow water known as Lake Onalaska, which also receives the waters of the Black River upstream from Brice Prairie. Determination of the nutrient levels in Lake Onalaska and the effects of such navigation pools on them, constituted the bulk of this study. METHODS AND MATERIALS

Sampling:

Samples fot' this study were collected on a bi-monthly basis from March 12 to October 1, 1972. Sampling sites were selected in an attempt to monitor any changes in water quality occurring between the upstream and downstream margins of Navigation Pool No. 7. Location of all sampling sites is found on Figure 1. Site I was located below Lock and Dam No. 7 at Dresbach, Minnesota. Water samples. were collected in the tail- water area where thorough mixing of the water in the main channel occurs as it passes through the locks. Site II was located two meters off shore at the tip of French Island, La Crosse, Wisconsin. The island extends as a narrow point into Lake Onalaska. Samples from this site would be representative of water from the center of the lake. Site III was located below the concrete spillway at the downstream end of Lake Onalaska, Onalaska, Wisconsin. Water is well mixed as it passes over and under the spillway, and these samples would be representative of the waters that have passed through Lake Onalaska. Site IV was located at the end of a ten meter pier at the Public Boat Landing, Brice Prairie, Wisconsin. These waters are at the upstream end of Lake Onalaska and are relatively unaltered since entering the lake from the Black River. Although water quality varied from week to week, this study attempted to monitor seasonal fluctuations in water quality as well as water quality differences which existed within the navigation pool.

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All samples were collected at a depth of one meter using a Kemmerer .water sampler. Water sample temperature was measured and the samples were transferred immediately to one-liter polyethylene bottles. Samples were transferred to the laboratory in the dark at OOC. All samples were collected ciose to mid-day to eliminate diel fluctuations in water quality. In the laboratory, large suspended matter was removed with a

pre-filter pad. The sample was then filtered using a .045 ~ .02 ~ HA Millipore -Rr filter that had been pretreated by passing 50 ml of distilled $ water through it. This porosity was chosen because of its ability to remove all nannoplankton (Goetz and Tsuneishi, 1951; and Lasker, 1957). Each sample was divided into 6-25 ml samples which were placed in screw- capped 125 ml Erlenmeyer flasks. The remaining filtrate was used far chemical measurements and preparation of inocula.

Chemical measurements:

3 The pH, alkalinity, nitrate (No 3-l) and phosphate (Po 4- ) were determined for each sample. The pH of the samples was measured using a 2 Beckmann Zeromatic IIR . Alkalinity was determined using the titration . method with methyl orange as the indicator (American Public Health Association, 1960). The total inorganic carbon available was determined from the alkalinity by use of a conversion table (Saunders, G. W., E. B. Trama and R. W. Bachman, 1962). Nitrate and phosphate were 3 measured colormetrically using a Spectronic 20R •

Rl - Millipore, Bedford, Mass. R2- Beckmann, Fullerton, Calif. R3 - Bausch and Lomb, Chicago, Ill. -9-

Production of inocula:

Organisms used as inocula were Scenedesmus guadricauda and Chlorella vulgaris. These organisms were maintained in pure stock cultures and used individually as inocula. Such procedures removed the possibility of retardation of photosynthesis by growth inhibiting substances and algal antibiosis (Pratt, 1943; Proctor, 1957). Stock cultures were maintained in 30 ml of nutrient medium in a 125 ml Erlenmeyer flask {Bueltman, 1969). Every other day, one ml of stock culture was added to another culture flask. Only eight-day old cultures were used for inocula. Incubation of the test flasks and maintenance of stock cultures were under identical controlled environmental conditions. Temperature was maintained at 24°C + l°C. Illumination was by fluorescent lighting providing 380ft-cat midpoint of the culture flasks. All flasks were continually shaken at 60 strokes per minute by a reciprocating shaker.

Preparation of inocula:

An eight-day old stoc~ culture was centrifuged and the supernatant discarded. Sedimented cells were resuspended in 50 ml of filtered sample water and again centrifuged. Sedimented cells were then resuspended in sufficient filtered sample water to yield the following concentrations of cells for the inoculum: Chlorella, 5.0 x 10 6 cells/ml and Scenedesmus, 5.0 x 10 6 cells/ml. These cell concentrations were determined using a hemacytometer. Once the cell concentrations were determined, the 1 samples were placed in a Hach Laboratory TurbidimeterR and the values recorded. Thereafter, inoculum was prepared by adding sample water to

Rl - Hach, Ames, Iowa. -10- the sedimented cells until turbidity readings corresponded to the appropriate cell concentrations. Control flasks were also established using growth medium for inoculum preparation.

Preparation of test flasks:

Filtered sample water was added in 25 ml aliquots to each of 6 test flasks. Three flasks were used for each algal species; two light flasks and one dark. One ml of inoculum was added to each flask and

14 14 • a predetermined amount of C was added as NaHC 03 One-tenth micro curie of NaHC 140 /mg inorganic C was added by use of a hypodermic 3 syringe inserted deep into the test sample. Samples were incubated for one hour under the standard conditions described above.

Preparation of the sample for counting:

After incubation, the contents of each test flask were filtered through a 0.45 ~ .02 ~ MilliporeR 1 filter. Each flask was washed with a 5 ml distilled water which was also poured through the filter. Filters were allowed to air dry before counting. Dried filters were assayed for radioactivity using a Nuclear-ChicagoR2 Model 470 gas flow counter of known efficiency. Filters were counted for a two-minute period. For each sample, light counts were averaged and the dark counts subtracted. The count was then corrected for the efficiency of the machine. The amount of carbon fixed by photosynthesis was determined from the relationship:

Rl - Millipore, Bedford, Mass. R2 - Nuclear-Chicago, Des Plaines, Ill. -11-

12c available 14c available ~~--~~~~ = K X 12c assimilated 14c assimilated where: l2C available = mg inorganic carbon present in test flask 12C assimilated = mg carbon fixed by photosynthesis in the test flask K = 1.06, a factor which corrects for the slower uptake of 14C compared to 14C 14C available = the amount of 14C added to the test flask at the start of incubation

14C assimilated= average counts per second on the light filters less the dark filter counts per second corrected for the counter efficiency

Correction was not made for self absorption due to the small quantity of algae involved (Goldman, 1960). Natural and cosmic background radiation from the machine are eliminated from consideration by the use of the dark samples. RESULTS AND DISCUSSION

Primary productivity, the net rate of fixation of organic carDon by photosynthesis, was taken to be a measure of the relative eutrophic state of the waters from the four sampling sites. Values for primary productivity of Scenedesmus guadricauda and Chlorella vulgaris at Site l, Dresbach, are found on Figure 2 and Table 1. The data indicated that for both test species the maximum productivity, 11.22 for Scenedesmus and 4.89 for Chlorella, occurred in March. Minimum values for Scenedesmus and Chlorella were reached in late spring (May-June), early July and August. Both species demonstrated an increase in productivity in July and late September.

Site II (French Island) demonstrated fluctuations in productivity levels similar in pattern to those found at Site I {Fig. 3, Table 2). March is the time when both species exhibited maximum productivity, 11.21 for Scenedesmus and 5.26 for Chlorella. At this site, both test species exhibited a maximum productivity in mid-July, as was the case at Site I. Two periods of low productivity were noted. The minimum values for both species occurred in early May (Scenedesmus, 2.70 and Chlorella, 1.78). Early July, August and early September demonstrated minima. The increase in late September at this site was not marked.

Site III (Lake Onalaska spillway) exhibited the same pattern as Sites I and II (Fig. 4, Table 3). Both species demonstrated productivity levels in March which were in excess of those found at any sampling site

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(Scenedesmus, 11.57 and Chlorella, 8.93). In May, this site recorded the lowest productivity levels found at any site (Scenedesmus, 1.77 and Chlorella, 1.37). An additional minima was noted for both species in August. Marked increases were noted in productivity values recorded in July and late September.

Date for Site IV (Brice Prairie) indicated the range of productivity levels for the test species was not as great as it was at Sites I, II, and III, but the patterns were similar (Fig. 5 and Table 4): Maximum values for both species (Scenedesmus, 10.50 and Chlorella, 7.44) were again noted in March. Minima were recorded in May and August, while increases in productivity levels occurred in July and late September.

The data indicated that for all sampling sites, productivity values were at a maximum in March. Hutchinson (1957), Pearsall (1930), and Domogalla (1926) all reported high productivity levels in early spring when nutrient levels and incident light values were high. These authors, furthermore, reported minimum productivity occurring in late spring (May) and mid-summer (August). These findings are consistent with the low productivity values reported by this author for these periods. All sampling sites demonstrated increases in productivity in July and late September. These increases were probably in response to increased nutrient levels, which will be discussed below. An analysis of variance was run on the productivity values to determine if a significant difference existed between the means of the· productivity values for the four sites, and the results were negative.

1 The nutrients examined at each sampling site were nitrogen (N0 3- ) and phosphorus (P0 4-3) expressed in mg/1. Nutrient levels at Site I -14-

(Dresbach, main channel) showed a marked seasonal variation (Fig. 6, 1 Table 6). Nitrate (N0 3- ) levels were at their highest levels in March, mid-June and late September. The maximum value recorded was 4.8 mg/1. During July and August the nitrate levels fell to their minimum values

- 3 ) (0.9-1.3 mg/1). Phosphate (Po 4 levels followed a pattern similar to that of the nitrates. Maxima were noted in March, June and September (0.5 and 0.6 mg/1) respectively. Minima were observed in April and May and again in July-August. The minimum level of P0 4 was 0.1 .mg/1 in July.

Water collected at Site I is representative of water of the main channel of the Mississippi River. In an examination of the hydrology of the Navigation Pool No. 7, Claflin (1974) reported that current patterns from the main channel into Lake Onalaska are minimal due to their reduction by a chain of islands which parallel the flow of the main channel. Lake Onalaska tends, therefore, to be isolated from the main' channel system. The small volume of water entering the pool from the Black River is not sufficient to establish currents within Lake Onalaska. Hydrologically, physically and chemically, Lake Onalaska resembles a typical eutrophic lake. Concerning nutrient dynamics, it is significant to note that the waters of the main channel and the pool appear to function independently. In studies conducted on nutrient levels in the pool and main channel in 1967 and 1971, Claflin (1974) noted that correlation coefficients for nitrates and p~osphates between the main channel and the pool were poor. Correlations for nitrogen were r = 0.316 (1967) and r = 0.344 {1971), and correlations for phosphorus were r = 0.344 (1967) and r = 0.564 (1971). It was concluded that nutrients -15- within the navigation pool were cycled and released independently of the main channel.

Nutrient levels for Site II (French Island) revealed two maxima for nitrate levels (Fig. 7, and Table 2) .. The highest levels recorded were 4.8 mg/1 in late June and 2.8 mg/1 in March. The months of Apt·il, July and August demonstrated minimum values. In mid-August, the lowest nitrate level (0.5 mg/1) was recorded. Phosphate levels at this site varied in pattern from nitrate levels. Maximum values (0.4 ~mg/1) were recorded in both March and September. The minimum value recorded (.05 mg/1), occurred in mid-August.

At Site III (Lake Onalaska) nitrate levels fluctuated in a similar fashion to those at Site II (Fig. 8, Table 3). Maximum values are recorded in March (5.4 mg/1) and June (3.7 mg/1). The months of July and August are characterized by low nitrate levels. The minimum value recorded is in mid-August (.05 mg/1). It appeared that nutrient levels increased in the month of September. Phosphate levels also reach their maxima in March (0.4 mg/1), June (0.4 mg/1) and September (0.4 mg/1) . . Minimum values are recorded in May (.05 mg/1) and July (.05 mg/1).

At Site IV (Brice Prairie), nutrient levels exceeded those recorded at any other site (Fig. 9, Table 4). The pattern noted at Sites II and

III for changing nutrient levels was repeated at this site. Nitrate values were at a maximum in March (5.9 mg/1), June (4.9 mg/1) and September (2.3 mg/1). Minimum values were noted in July and August (0.1 mg/1). Phosphate levels fluctuated in a similar fashion to nitrate levels. Maxima were noted in March (0.6 mg/l), June (.55 mg/l) and September (.5 mg/1). The minimum value is again noted in mid-August (0.1 mg/1). -16-

The high nutrient levels found in March at all sampling sites would accompany the vernal circulation and run-off entering the drainage basin. It is assumed that large quantities of allocthonous nutrients from agricultural and domestic drainage reach the navigation pool during the spring runoff.

Hutchinson (1941) found great variation in the nutrient content of a lake during the period of summer stagnation. All sites within the navigation pool demonstrated a maximum value occurring in late June. Examination of precipitation records for the drainage area did not indicate a relationship with the increased nutrient levels occurring in mid-summer. Increased nutrient levels must be accounted for by some mechanism releasing autochthonous nutrients.

The rise in temperature in the summer months would result in increased decomposition of organic matter, rooted vegetation and phyto plankton. The biomass of rooted vegetation within Lake Onalaska was reported by Claflin (1974) to range from 120 g/m 2 to 540 g/m 2 . The species most frequently encountered were Ceratophyllum demersum, Elodea canadensis, and Potamogeton crispus. The dense stands of rooted vegeta tion tend to reduce current through the pool and to minimize wave action. Hutchinson (1957), Boyd (1970), and Oswald (1957) reported on the ability of rooted aquatic vegetation as well as algae to assimilate nitrates and phosphates. The assimilation and release of nutrients by plants may thus significantly affect their concentrations in a body of water. This author would attribute the increased nutrient levels in mid-summer to the decay of the abundant plant life and subsequent release of nutrients trapped within them into the water column. Due to the depth of the navigation pool, it is unlikely that thermal stratification or a loss of -17-

the oxidized-microzone at themud~water interface occurred. Release of nutrients from the sediments thus appeared unlikely.

The relative state of eutrophy of a body of water could be established if a significant correlation was found between nutrient levels and productivity in an algal assay procedure. Tables 5 and 6 give the correlation coefficients between the test species and nitrate and phosphate levels recorded on nineteen sampling dates. The data indicate that no significant correlation existed between nutrient levels and productivity. Several factors may account for these results: The nutrient levels recorded on all sampling dates were in excess of the minimal concentrations permitting optimal growth of various species .of algae (Chu, 1943). Chu reported that there was a wide range of concentrations at which further increases of phosphorus had no effect on the growth rate of algal populations. Weiss (1971), in an evaluation of the algal assay procedure utilized in part by this study, stated that it was essential to establish the response of algae _to kn~wn _ nutrient levels. Weiss reported that significant differences in responses of the test organisms were· noted in media with high nutrient levels. Productiyity of the test species may have been further affected by the transfer of the algae from the growth medium to the test waters due to a time period needed for acclimation.

Examination of the data for productivity, nitrate and phosphate levels does reveal some of the nutrient dynamics occurring within the navigat1on pool. Mean primary productivity values for the four sites are found on Table 7. Station IV (Brice Prairie) demonstrated the highest productivity value (4.52 mgC/1/hr) recorded. A test of signifi- -18- cance (T test) was run on paired sites to determine if a significant difference in productivity existed, Site IV showed significantly greater (0.1 or less) productivity than either Site II or III. Site I and Site IV functioned independently of each other regarding nutrient cycling and the differences in their productivity was not significant (0.7).

Significant differences in nutrient levels are also noted between various sites. Site IV exhibited the highest mean nitrate ievel of all sites (2.96 mg/1). A significant difference (0.2-0.1) exists between Site IV and Site III (Table 8). Comparison of Site IV and Site II values revealed a 0.1-0.5 level of significance between nitrate levels.

Tests of significance were run on all paired sites for phosphate levels (Table 9). Site IV (Brice Prairie) again exhibited the maximum mean phosphate level (.33 mg/1). Levels of significance between this site and sites II and III indicated levels of significance of 0.01.

Site IV is upstream from Sites II and III (Fig. 1). Although no detectable currents existed, water entering Lake Onalaska from the Black River would pass in a direction from Site IV towards Site II and III. As noted earlier, water passing through the navigation pool is in contact with extensive vegetation. The date indicated that water entering the pool (Site IV) is significantly richer in nutrients and demonstrated a significantly greater productivity than water sampled downstream (Sites II and III). It seems apparent that the extensive rooted vegeta tion and phytoplankton within the pool functioned as a nutrient trap by assimilating nutrients into plant tissues. Decay of these plants added significant quantities of nutrients to the water column as well as to -19-

the sediments of this navigation pool. It thus appears that a definite cyclic phenomena existed within Lake Onalaska. The phenomena of nutrient cycles within the navigation pool should be of value to those concerned with the assessment of the environmental impact of the navigation pools.

Conclusions: 1. Productivity values attained maximum levels at all sites in March. Other maxima were noted at all sites ·in early July and late September. 2. Productivity values were minimal in May, June and in late July and August. 3. Nutrient levels reached maximum levels in March. Other maxima were noted in June and in late September. 4. Nutrient levels were at a minimum in May, June and August. 5. No significant correlations were detected between productivity values and the nitrate and phosphate levels observed. 6. Productivity values, nitrate levels and phosphate levels were ·significantly higher (0.1) at Brice Prairie (Site IV) than at French Island (Site II) or the Onalaska spillway (Site III). 7. The standing crop of rooted vegetation and algae within Navigation Pool No. 7 was extensive and appeared to be effective in removing nutrients from the waters of the navigation pool. 8. No significant differences were noted between waters at the downstream end of Lake Onalaska.

9. No significant differences were found to exist between waters ~f the main channel and those of Lake Onalaska even though they have different sources of origin. -20-

11 11 10. Navigation pools appear to be an effective nutrient trap • Incoming nutrients were apparently assimilated into the abundant plant growth and subsequently trapped within the sediments of the navigation pool. Decay of this vegetation appeared to be responsible, in part,

for c~clic nutrient phenomena within the pool~

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SELECTED REFERENCES

American Public Health Association, 1960. Standard Method for the Examination of Water and Sewa~ (lOth Ed . ), Am. Public Health Assoc., New York, N. . Y. 57Z pp. . Bartsch, A. F., 1969. Accelerated eutrophication of lakes in the United States: Ecological response to human activities. Envir. Pollut., l (2): 133-140. Boyd, C. E., 1970. Vascular aquatic plants for mineral nutrient from polluted waters. Econ. Bot . , 24: 95-103 . Bueltman, C. G., 1969. Provisional Algal Assay Procedure. Joint Industry/Government Task Force on Eutrophication, New York. 62 pp. Chu, S. P., 1943. The influence of the mineral composition of the medium on the growth of planktonic algae. Part II. The influence of the concentration of inorganic nitrogen and phosphate phosphorus . J. Ecol., 31: 109-148. Claflin, T., 1974. Environmental Assessment Study, Navigation Pool No. 7, Upper Mississippi Ri ver , St. Paul District, U. S. Army Corps of Engineers. Domogalla, B. P., Juday, C., and Peterson , W. H., 1926. Seasonal variations in the ammonia and nitrate content of lake waters. J. Amer. Wat. Wks. Ass., 15: 369-395. Fremling, C., 1973. Environmental Impact Study of Pool No. 6 of the Northern Section of the Upper Mississ i ppi River Valley. Unpublished. Goetz, E., and Tsuneishi, C., 1951. The application of molecular filter membranes to the bacter ial analysis of water. J. Amer . Waterworks Assoc., 43: 943-969. Goldman, C. R., 1960. Primary productivity and limiting factors in three lakes of the Alaska peninsula. Ecol. Monog., 30: 207-230. Goldman, C. R., 1963. The measurement of primary productivity and limiting factors in freshwater with C-14, Proc . Conf. on Primary Productivity t~easurement., U. S. A. E. C. T. D.-7633. Hasler, A. D., 1947 . Eutrophication of lakes by domestic drainage. Ecol., 28: 383-395. Hutchinson, G. E., 1944. Limnological studies in Connecticut VII. A critical examination of the supposed relationship between phyto plankton periodicity and chemical changes in lake waters. Ecol., 25: 3-26. -22-

Hutchinson? G, E., and Bowen, V. T., 1950 , Limnological studies in Connecticut, IX. A quantitative radiochemical study of the phosphorus cycle in Linsley Pond ; Ecol., 31: 194-203' .. Hutchinson, G. E., 1957 . A Treatise on Limnology. New YorKl J. C. Wiley and Sons. 1015 pp . Ketchum, B. H. and Redfield, 1949. Some physical and chemical character istics of algae grown in mass culture. J. Cell. and Comp ; Physiol., 33: 281-300. Lasker, R. and Holmes, R. W., 1957. Variability in retention of marine phytoplankton by membrane filters. Nature, 180: 1295-1296. Lindeman, R. L., 1942. The trophic-dynamic aspect of ecology. Ecology, 23: 399-418. MacFayden, A., 1948. The meaning of productivity in biological systems. J. Anim. Ecol., 17: 75-80. Oswald, W. J., 1957. Algae in waste treatment. Sewage Ind. Wastes, 29: 437-455. Pearsall, W. H. , 1930. The proportions in the waters of some dissolved substances of biological importance. J. Ecol., 18: 306-320. Potash, M., 1956. A biological test for productivity. Ecol., 37: 631-639. Pratt, R., 1943. Studies on Chlorella vulgaris VI. Retardation of photosynthesis by a growth-inhibiting substance from Chlorella .vulgaris. Am. Jour. Bot., 30: 32-33. Proctor, V. W., 1957. Studies of algal antibiosis. Limn. and Ocean. 2: 125-139. Saunders, G. W., F. · B. Trama and R. W. Bachman, 1962. Evaluation of a modified C-14 technique for shipboard estimation of photosynthesis in large lakes. Mich. Univ. Great Lakes Research Division, Publ. No. 8. 61 pp. Steeman Nielsen, E., 1951. Measurement of the production of organic matter in the sea by means of carbon-14. Nature, 167: 684-685. , 1952. The use of radiocarbon (C-14) for measuring ------~----~ organic production i~ the sea. J. Cons. Int. Explor. Mer., 19: 309-328. U. S. Army Corps of Engineers, Master Recreation Plan Part IX- Pool No. 7, St. Paul District, U. S. Army Engineer District, St. Paul, Minnesota . . 29 pp. Verduin, J., 1956. Energy fixation and utilization by natural communities in Western Lake Erie. Ecol., 37: 40-50. ~23-

Weiss, C, W., 1971. The Interlaboratory Precision Test; An Eight Laboratory Evaluation of the Provisional Algal Assay Procedure Bottle Test. U. S. Govt. Printing Office. 70 - pp~

• •

APPENDIX -24-

nitrate _(N0 -I), and phosphate Table 1: Primary productivity (mgC/1/hr), 3 (Po - 3 ) levels in Navigation Pool No . 7, recorded at Site 4 I ' Lock and Dam No. 7, Dresbach, Minnesota, 1972. Primary productivity (mgC/1 /hr) · Scenedesmus Chlorella N0 - 1 (mg/l) P0 - 3 (mg/l) Date guadricauda vulgaris 3 4

3/12 11 . 22 4.89 3.3 .3 3/27 5.02 3.34 1.8 .3

4/3 7.92 3.09 2.75 • ..3 4/18 4.98 2.90 3.9 .2 4/23 6.03 3.48 1.2 .3 5/2 3.23 2.15 1.2 .2 5/14 3.78 2.19 2.1 .2' 5/29 4.08 2.68 2.3 .3 6/12 6.25 3.58 3.5 .5 6/18 5.54 3.42 4.8 .2 · 6/26 . 4.66 2.85 2.7 .3 7/3 4.82 .83 1.3 . 1 7/17 6.90 4.04 1.1 .2 8/1 . 5.11 2.73 .9 .2 8/14 5.32 3.32 .9 .3 8/24 4.78 3.74 1.0 .3 9/2 5.22 3.32 1.8 .4 9/10 6.22 3.51 2.8 .6 9/24 6. 94 . 3.60 2.6 .4 -25-

Table 2: Primary productivity (mgC/1 /hr), nitrate _(N0 3 ..-1), and phosphate - 3 } (Po 4 levels in Navigation Pool No. 7, recorded at Site II, on French Island, La Crosse, Wisconsin, 1972. Primary productivity (mgC/1/hr) Scenedesmus Chlorella N0 - 1 (mg/l) P0 - 3 (mg/l) Date guadricauda vulgaris 3 4

3/12 . 11 . 21 5.26 2 ..8 .4 3/27 9.62 4.54 2.6 .3 4/3 6.83 3.9 2.0 .2 4/18 4.42 3.34 1.0 .2 4/23 3.68 2.64 2.2 .3 5/2 2.70 l. 93 2.0 .2 5/14 2.58 1.78 1.9 .05 5/29 3.28 l. 93 3.0 . 1 6/12 4.62 3.35 2.8 .2 6/18 5.61 3. 72 4.8 . 2 . 6/26 5.30 2.86 3.4 . 1 . 7/3 4.42 · 1.03 1.1 .05 7/17 6.86 3.49 1.3 .2 8/1 . 5.01 2.88 .6 . 1 8/14 5.27 2.67 .5 .05

8/24 4.02 2.45 .8 ~3 9/2 4.22 2.74 2.1 .3 9/10 5.66 3.01 1.8 .4 9/24 5.35 3. 21 1.5 .3 -26-

Table 3: Primary productivity (mgC/1/hr), nitrate (N0 3-l), and phosphate (PO 4 -3) levels in Navigation. Pool No , 7,. recorded at .Site III, the Onalaska Spillway, Onalaska, Wisconsin, 1972. Primary productivity (mgC/1/hr) Sceriedesmus Chlorella N0 -I(mq/l) P0 -3(mg/l) Date guadricauda vulgaris 3 4

3/12 11.57 8.93 5.4 .4 3/27 9.91 4.11 5.3 .35

4/3 7.16 4.39 4.8 • .3 4/18 4.34 2.37 2.3 .2 4/23 4.87 2.80 2.8 .3 5/2 2.33 1.85 2.0 .2

5/14 1.77 l. 37 2.8 .05 . 5/29 1.94 1.14 2. 1 ... 15 6/12 4.26 2.59 1.6 .2 6/18 4.80 3.02 3.7 .4 6/26. 5.47 2.80 2.8 . 1 7/3 5.57 1.07 .9 .05 7/17 6.22 3.23 .8 .3 8/l 4.05 1.63 .3 . 15 8/14 3.90 l. 60 .05 .2 8/24 5. 01 2.02 .6 .25 9/2 5.12 2.50 1.6 .3 9/10 5.48 3.24 2.4 .3 9/24 . 5. 88 . 3.42 2. 1 .4 -27-

Table 4: Primary productivity (mgC/1/hr), nitrate ~N0 3 -l), and phosphate (Po -3) levels in Navigation Pool No. 7, recorded at Site IV, the 4 Brice Prairie Boat Landing, Brice Prairie, Wi scans in, 1972. Primary productivity {mgC/1/hr) ·scenedesmus Chlorella No -l(mg/l) Po - 3 (mg/l) Date guadricauda vulgaris 3 4

3/12 10.50 7.44 5.9 .6 3/27 8.50 5.62 5.7 .4 .. 4/3 8.22 3.57 2.3 .3 4/18 5.16 2.70 4.75 .2 4/23 4.89 2.94 1.6 .3 5/2 3.55 2.24 1.5 .2 5/14 3.94 2.84 2.4 .2 5/29 4.03 2.32 2.4 .2 6/12 5.16 2.86 3.9 .4 6/18 4.37 3.35 4.9 .55 6/26 . 4.73 2.84 2.0 .2 7/3 5.11 1.89 1.8 .2 7/17 . 6.18 . 3.34 2.0 .3 8/1 3.79 2.55 1.2 .2 8/14 4.07 2.25 1.0 . l 8/24 4.62 2.82 1.3 .2 9/2 6.10 2.62 1.9 .4 9/10 6.82 3. 72 2.0 .5 9/24 7.08 3.90 2.3 .5 -28-

Table 5. Correlation coefficients (r) between productivity of test species - 1 ) and nitrate (No 3 levels in Navigation Pool No. 7, 1972.

Sampling Site Scenedesmus Chlorella guadricauda vu1gans

I, Dresbach .13 '14 II, French Island . 12 .27 Ill, Onalaska Spillway .66 .76 IV, Brice Prairie .64 .75

Table 6. Correlation coefficients (r) between productivity of test species and phosphate (Po 4-3) levels in Navigation Pool No. 7, 1972.

Sampling Site Scenedesmus Chlorella guadricauda vulgaris

I, Dresbach .24 .49 II, French Island . 57 .63 III, Onalaska Spillway .65 .76 IV, Brice Prairie .73 .75 -29- -30-

fable 8. Test of significance between nitrate (N0 3-l) values observed at Brice Prairie Public Boat Landing and several sites in Navigation Pool No. 7, 1972 ~

Mean nitrate (No - 1 ) T value Level of )ampl ing Site 3 1eve 1s, (mg/1 ) d.f. = 18 Significance

IV, Brice Prairie 2.96 1 .. 52 .2-.1 III, Onalaska 2.54

IV, Brice Prairie 2.96 • 1.88 .1-. 05 II, French Island 2.17

IV, Brice Prairie 2.96 1.01 0.3 I, Dresbach 2 ..77

Table 9. Test of significance between phosphate (Po 4 -3) values observed at Brice Prairie Public Boat Landing and several sites in Navigation Pool No. 7, 1972.

3 Sampling Site Mean phosphate (P0 4 - ) T value Level of levels, (mg/1) d.f. = 18 Significance

IV, Brice Prairie .33 3.50 .01 III, Onalaska .25

IV, Brice Prairie .33 3.82 . 01 II, French Island .23

IV, Brice Prairie . 31 -.12 0.9 I, Dresbach .31 W I S C 0 N S I N "'

0 ~ LAKE

I w

M I N N E S 0 T A

e Site I, Lock and Dam No. 7, Dresbach, ~1innesota c 0 R p Site II, French Island, La Crosse, Hisconsin s • 0 F Site Ill, Onalaska Spillway, Onalaska, Wisconsin E N ... G I N Site IV, Rrice Prairie Public Ro~t Landin~, E Brice Prairie, '!i sconsin LOCATION OF DREDGE CUTS E • AND SPOIL DEPOSITS FOR POOL 7 ~

1------ST. PAUL DISTRICT I 9 ~~9~ Figure 1. Location of sa~pling sites in Nav i"ation Pool No. 7, 1972. 11.0 10.0 • Scenedesmus guadricauda 9.0 C\ 0 Chlorella vulgaris I \ 8.0

7.0 1: 6.0 ...... - ...... u 5.0 C"l E ...... - I w j "e-41 _j N 4.0 L~ \ t'\ I 3.0 2.0

1.0

Figure 2. Primary productivity (mgC/1/hr) for Scenedesmus guadricauda and ~hlorella vulgaris at Site I in Navigation Pool No.7 at Lock and Dam No.7,Dresbach,Minnesota, 1972. 11 . 0 10.0 t • Scenedesmus guadricauda 9.0 0 Chlorella vulgaris I \ 8.0 " 7.0 s...... c: ...... 6.0 ....- ...... u en 5.0 E I ..... I ...... ~ I I I " ' w w 4.0 I -...... " ? .-- I I 3.0

2.0 1.0

Figure 3. Primary productivity {mgC/1/hr) for Scenedesmus guadricauda and ~hlorella vulgaris at Site II in Navigation Pool No.7 at Frerich Island,LaCrosse,. Wisconsin,l972. 11.0 10.0 I ". 4t Scenedesmus guadricauda 9.0 - ,... I . 0 Ch1orella vulgaris 8.0

].0

s.. ..s::: 6.0 ...... r-...... ~ 5.0 - I E w _,., \._ +:. 4.0 I ~ ~ . / I I

3.0

2.0 1.0

Figure 4. Primary productivity (mgC/1/hr) for Scenedesmus guadricauda and Chlore1la vulgaris at Site III in Navigation Pool No.7 at the Onalaska Spillway,Onalaska, Wisconsin,l972. 11.0

10.0 r= • Scenedesmus guadricauda 9.0 Chlore11a vulgaris \__ 0 8.0

7.0 s... .s:: 6.0 .-- -u Q') 5.0 I -E w U1 4.0 I \ ~ \ ~ I I 3.0 ' 2.0

1.0

Figure 5. Primary productivity (mgC/1/hr) for Scenedesmus guadricauda and Chlorella vulgaris at Site IV in Navigation Pool No.7 at the Public Boat Landing, Brice Prairie, Hisconsin, 1972. ,., -I I I I I I I I I I I I 6.0 ' ' 5.0

..... 4.0 .-- 3.0 O'l ...._,-E ...... 2.0 ~ ("'() 0 1.0 z

I w 0'1 .6 1- I I I I J I I I I I I I I n I . 5 '-t .4

~ .. 3 O'l ...... E . 2 ("'() l..:t 0 . 1 0..

' 3 'I Figure 6. Nitrate(N~-}) and phosphate (Pcr4 ) levels (mg/1) at ~ite I in Navigation Pool No. 7 at Lock and Dam No.7, Dresbach ,~1i nnesota, 1972. .lj

I i

! ~ !. ~] -- 6.0 I I I I I I I ' I ' I I I I I 5.0

...... 4.0 r- ...... O'l 3.0 E ...... 2.0 ICY'l 0 z 1.0

M M A A M M Jn Jn Jl Jl A A s s

I w ...... • 6 I . 5 .4 .. - ...... 3 O'l E

(Y') .2 l.:t 0 . 1 0...

Figure 7. Nitrate (NOj 1 ~nd phosphate(P0i3)levels (mg/1) at Site II in Navigation Pool No.7 at French Island, -LaCrosse,Wisconsin,l972. 6.0 5~0

...... 4.0 r- 3.0 O'l E -'--' 2.0 ...... 1 en 0 1.0 z

M M A A M M Jn Jn Jl Jl A A s s

I w I 1..0 .6 ! . 5 .4 ...... 3 O'l E . 2 -'-' en I ..::I" 0 . l 0..

Figure 9. Nitrate (No;1)and phosphate (P043)levels (mg/1) at Site IV in Navigation Pool No.7 at the Public Boat Landing, Brice Prairie, Wisconsin,l972.

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