Skip to Navigation | Skip to Content

Plankton Community in North Pond


James DeYoung and Steve Dyk | December 11, 1998 | Biology 345

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


INTRODUCTION

After the fish kill in Ravenswood Pond last spring, many questions about the health of the ponds on campus were raised. One way to get an evaluation of the health of the ponds is to look at the plankton communities living in these ponds. Plankton are the big oxygen producers in pond systems, so counting and identifying them is important. North Pond is one of the largest ponds on campus, and being distant from the other two ponds it exists as a good control. In doing these types of tests and evaluations, a focus on gaining a better understanding of the types of plankton occupying North Pond was achieved.

METHODS

Methods included three main areas: collecting, identifying, and counting. Collecting consisted of excursions to North Pond utilizing a plankton net (Wild Co. 025125 47-L), a canoe, sampling jars, and oars. Two samples were drawn at each of the two sites located in the middle of the southern and northern halves of North Pond (Map). Collecting started by rowing to the certain destination desired and dropping anchor. The plankton net was lowered to the bottom of the pond and then drawn straight up collecting the organisms in that column of water. The excess water was drained out of the collecting tube and the remaining water and organisms were placed in a labeled jar. The two sampling sites were 1.5 meters deep. The two pulls drawn from each location were combined before they were surveyed.

The plankton were identified using a compound microscope (American Optical Fifty 772109 and Olympus CHT 6H0132), a Sedgewick-Rafter 1mL slide, and Needham's A Guide to the Study of Freshwater Biology. One ml of pond water was placed in a beaker with one ml of zooplankton preservative (4% Formalin with Glycerin) to immobilize the plankton which enhanced the likelihood of correct identification. Then one ml was taken out of the beaker and placed in the Sedgewick-Rafter slide with a cover slip in place. The slide was then placed under a microscope where the plankton were identified. Six random sites were chosen on each slide and the plankton were counted after their identification. Plankton were counted individually and tabulated in notebooks. The tabulated numbers were then calculated for the original volume of water.

RESULTS

The plankton of the pond were counted, and identified (table 1). The plankton were then compared according to the date sampled, and the weather change that occurred between the samples. Phytoplankton were greatly reduced in number, while the zooplankton were not as adversely affected by the drop in temperature(fig 1). The dominant phytoplankton species found in the pond water were Anacystis, Scenedesmus, Ankistrodesmus, Staurastrum, Polycystis, and Protococcus (fig 2). The dominant zooplankton species found in the pond water were Cyclops, Keratella, and Kirchenerellia (fig 3). The amounts of phytoplankton were more than double the amounts of zooplankton.

DISCUSSION

The zooplankton fared better than the phytoplankton after the cold since they are less sensitive to lower temperatures. The relationship between the phytoplankton and the zooplankton seemed to be less tied together than previously thought. The bigger decrease of the phytoplankton did not seem to inhibit the zooplankton in a significant way. This led to the conclusion that the zooplankton relied on other types of organisms for feeding, such as nanoplankton and bacteria. The big decline of the phytoplankton may have led to an increase of the bacteria that decomposes the dead phytoplankton. This increase in bacteria then ties into the fairly steady amount of zooplankton even after the weather change.

The incredibly large numbers of phytoplankton in North Pond led to a high turbidity. The major players in the phytoplankton were green and blue-green algae. This high turbidity led to a lower level of sunlight being able to penetrate into the lower depths of the pond, and therefore limiting the depth to which most of the phytoplankton could survive.

The different types of plankton found in the pond indicate the apparent health of the pond according to Standard Methods for the Examination of Water and Waste Water. The high levels of Staurastrum and Ankistrodesmus suggest a clean water atmosphere because they are normally found in oligotrophic lakes or bodies of water. Lower levels of Micrasterias and Pinnularia also indicate the clean water. A high amount of the Rotifer Keratella cochlearis was also found, which leads to the assumption that North Pond is not so far from the norm in that this species is the most frequently encountered among planktonic rotifers in North America.

This survey of the plankton community of North Pond led to a better understanding of the health of the pond and its components. North Pond seems to be overflowing with phytoplankton which leads to a high turbidity, but the certain species detected in the pond suggest a cleaner atmosphere than the initial outlook suggests. Another discovery was the interrelationship of the zooplankton and phytoplankton. The phytoplankton rely on the weather and amount of sunlight available in the pond, while the zooplankton rely more on the smaller producer base provided in the pond. Their relationship to each other is not that significant except for the dying off of the phytoplankton increasing the amounts of bacteria, which lead to a bigger food base for the zooplankton. The overall status of the pond seems to be relatively stable when looking at the dissolved oxygen content, nutrient availability, and the diversity of organisms contained in North Pond.

LITERATURE CITED

Cole, Gerald A. 1983. Textbook of Limnology. CU Mosby, London.

Eaton, Andrew D., Lenore S. Clesceri, and Arnold E. Greenberg. 1995. Standard Methods for the Study of Water and Waste Water. 19th Edition. American Public Health Association.

Needham, James G. and Paul R. Needham. 1962. A Guide to the tudy of Fresh Water Biology. Holden-Day, San Francisco.


FIGURES

click on any of the figures to see them full size

Map Figure 1
Figure 2

Figure 3


TABLES

TABLE 1 Plankton counts (per mL) in North Pond in the Ecosystem Preserve on the campus of Calvin College.

Plankton Types Sample on 9-29 and 10-1 Sample on 11-19
Phytoplankton    
Anacystis 286.4 210.9
Ankistrodesmus 138.1 73.5
Closterium 71.5 68
Coelosphaereum 32.1 62.4
Eurycerus 1.2 0
Microsterias 1.2 0
Nitzschia 1.2 1.4
Pediastrum 29.6 13.9
Pinularia 1.2 0
Polycystis 209.7 149.9
Protococcus 159.1 66.6
Scenedesmus 373.3 0
Selenastrum 3.7 0
Spirulina 1.2 0
Staurastrum 398.4 93
Stauroneis 2.5 0
Synedra 78.9 0
Volvox 2.5 0
     
Zooplankton    
Anabaena 1.2 0
Arcella 1.2 0
Asplanchna 2.5 0
Astasia 0 4.2
Bosmina 0 4.2
Camptocercus 4.9 0
Ceratium hirudinella 3.7 0
Chydorus 2.5 6.9
Cruciginia 8.6 0
Cyclops 23.4 123.5
Difflugia 0 18
Eubranchipus 0 9.7
Euglypha 0 1.4
Filinia 6.2 0
Gonatozygon 1.2 0
Hexartha opoliensis 2.5 0
Hydra 0 1.4
Kellicottia 0 1.4
Keratella cochlearis 58 69.4
Kirchneriella 287.4 0
Lecane 0 1.4
Mytilina 4.9 0
Nematode worm 1.2 0
Paramecium 1.2 1.4
Phormidium 1.2 0
Platyias 1.2 0
Polyphemus 1.2 0
Tabellaria 1.2 0
Trichocerca 2.5 0
Trinema 1.2 0
Zygnema 0 2.8