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Fluctuations in the Plankton Community of President's Pond, on the Calvin College Athletic Field.

Jennifer Call and Kim Romeyn | BIOL 345 | Fall 1998

Introduction | Materials and Methods | Results | Discussion | Figures | Tables


INTRODUCTION

Bodies of fresh water are inhabited by communities of phytoplankton and zooplankton. The presence (or absence) of different species that compose the community varies throughout the year, as do the numbers of individuals in each species. Aside from seasonal variations of temperature, rainfall and hours of sunlight, inputs of nutrients and/or contaminants may influence plankton populations. Therefore the study of plankton populations may help indicate the overall state of the water body. Phytoplankton especially is a good indicator of water quality (Eaton, 56).

In past seasons, plankton levels of various ponds on the Calvin College campus have been studied. During the Fall 1998 season, when our study took place, groups of students tested nutrient levels, inputs and outputs, and water quality of several bodies of water on Calvin's campus. Of special interest to us were those done on President's pond, which was where our plankton samples were taken from.

We were interested in the relationships between producer organisms and consumer organisms. George Reid (320-21) defines producers as "the organisms capable of synthesis of energy-containing organic substance through utilization of solar radiation and inorganic materials", and consumers as "the organisms, mainly animals, that are incapable of synthesis of matter from the sun's energy, and which depend directly or indirectly on the producers".

Growth of phytoplankton is dependant on certain nutrients (Barnes and Mann, 32). In areas with low content of electrolytes and organic matter, Plankton levels are low (Reid, 332), but in areas of high nutrient input, (sewage, fertilizer runoff), levels of algae (phytoplankton) can be quite high. After the Fall drop in temperatures, plankton levels tend to drop (Pennak, 176).

With these many variables, it is understandable that the levels in a particular body of water will fluctuate. But it is unrealistic to try to come up with a regular, predictable pattern for each species (Pennak, 176, 358).

METHODS

Study site:

President's pond is located in the Calvin College Athletic Field. It is to the south of Lake Drive, Grand Rapids, MI and to the east of Ravenswood pond, another body of water in the Athletic Field. During periods of heavy rainfall, the ponds overflow and join. Most of the water, besides rain, enters the pond from storm drains and runoff from higher areas. The deepest point of the pond is at the center, which is about 2.4 meters deep.

We decided to sample the plankton communities at three different locations on the pond (Fig. 1). Site A was chosen because of its close proximity to Ravenswood. As was mentioned previously, combining of the water can occur and there is potential for introductions of species from Ravenswood into President's pond. Site B was chosen to be the center of the pond. This was not only the deepest part of the pond, but also the most exposed to sunlight and wind. Site C was the north-east corner of the pond, nearest Lake Drive. The water here was shaded by the trees on the bank and quite protected from wind.

Experiment Our samples were taken between October 3 and November 13. Samples were taken on five occasions, approximately at one week intervals. Using a Wisconsin Plankton Net, (Wildco.USA. 018960), two trials from each sample site were taken. The water collected from the two trials was combined. The depths of the water columns sampled were recorded, as were the volumes of the water samples collected. (The samples from one site were not combined with the sample from another.)

Upon return to the lab, the samples were fixed with 10% Formalin solution (a phytoplankton preservative) in a 1:1 ratio. Then, using a Sedgwick Rafter counter cell, which holds 1 ml of liquid, six random fields were looked at under a compound light microscope. We looked at two slides from each of the water samples taken from the three sites. Identification of the organisms was done using An Introduction to Fresh Water Biology, by Needham and Needham.

Calculations

Mean counts of organisms were converted to number of organisms per mL of pond water. We determined the volume of the water column sampled and divided that number by the volume of water collected. That number was then used to divide the number of individuals found in the sample collected.

RESULTS

Interpretation of graphs

In correlating the data obtained from each of the three sites (figure 1) to the temperature and rainfall data (figure 2) for the Fall season, we notice that each site responds to the weather conditions differently. On October 3rd, Site C had fewer producers than consumers, while Sites A and B contained more producers than consumers. The data collected from October 9th shows that Site C had a significantly smaller number of producers than Sites A and B.

On October 16th ,there was a significant decline in both the producer and consumer populations for Sites A and B. While some decrease is noted in the producer and consumer populations for Site C, the decline is not nearly as significant. In addition, there is a significant decrease in the amount of producers compared to the amount of consumers.

Figure 2 illustrates significant rainfall on October 30th. On this sampling date, the producer and consumer populations of all three sites were reduced as a result of dilution. Site C contained roughly three times the amount of consumers as Site A, even though it contained roughly equal the amount of producers.

On the final date of collection, figure 1 portrays how the consumer populations exceed producer populations in both Sites A and C and are equal in to them in Site B.

Species Composition

At the beginning of the Fall season, figure 3 portrays that Polycystus was the most prominent producer in the plankton community by a considerable amount. Towards the end of the Fall season when temperatures had decreased, diversity of producers declined as well. The consumer population was dominated by Ceratium hirudinella (classified as a consumer because of its ability and habit of consuming producers) at the earlier portion of the Fall season. This species became extremely sparse at the date the final sample collections were made.

 

DISCUSSION

Data collected from sampling.

The data obtained from our experiment suggests that the plankton population was effected by variables such as temperature, rainfall, amount of available sunlight, etc. The factor causing Site C to contain fewer photosynthetic plankters than predatory consumers on October 3rd is because it's location at the north-east corner of President's Pond is shaded from sunlight for a significant part of the day. Receiving reduced amounts of sunlight is detrimental to producer growth. The amount of available sunlight accounts for the smaller amount of producers found in Site C on October 9th.

An increase in temperature on October 16th (figure 2) resulted in the decline in both producer and consumer populations in all three sites. In addition, temperature increase is the cause for the more significant lower producer levels found in Sites A and B. The assumption that producers are more sensitive to temperature change than consumers is supported by textual information (Barnes and Mann, 115).

In another study, a large number of planktivorus fish, namely the pumkinseed sunfish (Lepomis gibbosus), was collected from Site A around Oct. 30th. The removal of the predatory fish ( approximately1200 individuals) would be significant enough to decrease the zooplankton (consumer) species considerably (Lugan, Kolada, and Vander Ark, 1998).

Consumer populations can be supported by a smaller phytoplankton producer population because the consumers have an alternate food source: nanoplankton. Having a greater abundance of consumers than producers in a plankton population tells us that the consumers are not strictly dependent upon the phytoplankton (producers) as their sole source of nutrition.

Data collected from outside sources

Pond Productivity. Phytoplankton growth in President's Pond will be limited by the amount and availability of phosphorus because of the precise relationship between the concentration of total phosphorus and the standing crop of phytoplankton (Brower, Zar, and VonEnde, 146).

Water quality

Overall, President's Pond is in good condition. Any unhealthy areas are resulted from run-off of rain water from Lake Drive and area housing development. The urbanization of the watershed surrounding President's Pond increases the amount of excess nutrients and pollutants in the content of the pond (Berkompas and Bowersox, 1998).

It is difficult to draw ultimate conclusions about plankton levels from just one season's data. But, our data, when added to that collected in previous seasons, can be used to determine the overall health of President's Pond.

LITERATURE CITED

Barnes, R. K. , and Mann, K. H. 1980. Fundamentals of Aquatic Ecosystems. Blackwell Scientific Publications, Great Britain. 32.

Brower, Zar, and VonEnde. 1998. Field and Laboratory Methods for General Ecology, 4th Ed. McGraw-Hill Companies, Inc. Ch.10.

Cole, Gerald A. 1983. Textbook of Limnology, 3rd Ed. The C. V. Mosby Co., 56.

Eaton, Clescen and Greenburg. 1995. Standard methods for the Examination of Water and Waste Water. 15th Ed. American Public Health Assoc. 10-2

Needham, James G. and Paul R. 1962. A Guide to Freshwater Biology. Holden-Day, Inc.

Pennak, Robert W. 1978. Freshwater Invertebrates of the United States. 2nd Ed. John Wiley and Sons, Inc 176, 358.

Reid, George K. 1961. Ecology of Inland Waters and Estuaries. Reinhold Publishing Corp. 211, 320-321.


FIGURES

Figure 1 Figure 2
   
Figure 3 Figure 4

TABLES

TABLE 1 Species represented in at least one of three sites of October 3 through November 13 of the 1998 Fall season.

PRODUCERS   CONSUMERS
     
BLUE GREEN ALGAE   PROTOZOANS
Aphanocapsa   Ceratium hirudinella
Coeloshpaerium   Chilomonas
Phormidium   Codonella
Polycystus   Coleps
    Colpoda
GREEN ALGAE   Euglena
Botryoccoccus   Phacus
Crucigenia   Prorodon
Kirchneriella   Trinema
Microspora   Volvox
Mougeotia    
Pediastrum   ROTIFERS
Protococcus   Chromogaster
Scenedesmus   Filina
Spirogyra   Keratella sp.
Ulothrix   Testudinella
     
DESMIDS   CRUSTACIANS
Closterium   Bosminidae
    Bosmina
DIATOMS   Copopoda
Asterionella   Cyclops
Diatoma   Diaptomas
Fragilaria   Ostracoda
Navicula   Cypridopsis
    Nauplius larvae