Seasonal Changes of Plankton Species in
Lake Wingra
Ellen Bugg and Tori DeClerck
Introduction
- We studied the change in plankton communities throughout the seasons in
Lake Wingra to see how plankton populations are affecting the lake’s health.
- Plankton is the living fraction of material which floats in the sea or
freshwater. It is composed of microscopic plants-the phytoplankton-which are
predominantly autotrophic and are the primary producers of organic matter in
the aquatic habitats. The other type of plankton, the animals – zooplankton
– are the heterotrophic type of plankton, meaning they need to eat to gain
energy.
- A concern about plankton growth is that if there is too much to plankton
in the water it diminishes the water clarity. Reduced water clarity limits
the amount of light available for photosynthesis and leads to lower
dissolved oxygen concentrations.
- Our hypothesis is that the plankton will be more abundant in the fall
and spring and sparse in the winter.
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Methods
- We took plankton samples monthly from the dock of Lake Wingra by using a
plankton trap. We also recorded the temperature of the water with a
thermometer.
- We removed the plankton from the plankton trap and looked at samples
under a microscope.
- We then did a count of each type of plankton community we saw by sliding
the microscope from top to bottom and counting the number of each species of
plankton that we saw on 10x power.
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Results
- In our study, we found that that there was an abundance of plankton in
the fall months from October to November and those numbers reduced by
February (Table 1).
- There is not a big correlation between the total amount of plankton and
temperature but there is a slight change within each species.
- The number of blue/green algae is about the same for every month. The
number of crustaceans reduces gradually as the water gets colder. The number
of rotifers and green algae stays about the same between October and
November and reduces drastically in February. The protozoa are the complete
opposite, with small numbers in the fall and an increase in the winter
(Tables 1 and 2).
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Tables
Table 1. Number of Plankton counted from October to February
|
Date
|
Water Temp (degrees C)
|
Green Algae
|
Blue/Green Algae
|
Protozoan
|
Copepods
|
Rotifers
|
Diatoms
|
Cladoceran
|
Total
|
|
10/31/08
|
10.4
|
40
|
0
|
0
|
0
|
15
|
2
|
13
|
70
|
|
11/5/08
|
13
|
45
|
0
|
8
|
0
|
19
|
0
|
8
|
80
|
|
11/12/08
|
9
|
42
|
2
|
7
|
1
|
27
|
0
|
4
|
83
|
|
2/16/09
|
3
|
14
|
2
|
31
|
1
|
3
|
0
|
1
|
52
|
|
3/04/09
|
7.2
|
27
|
0
|
0
|
1
|
5
|
14
|
1
|
58
|
Table 2. Variations in Plankton count from October to February
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Conclusion
- Our hypothesis for this experiment was that there would be less
plankton in the winter than in the fall and spring. This was true for the
cladoceran, rotifers and green algae.
- There was an increase in protozoan between fall and winter. Diatoms
appeared in both October and March but they did not appear in the winter
months and there was no appearance of copepods in the fall but they appeared
in the winter months.
- The competition for food resources may have had an effect between the
correlation of rotifers and cladoceran. The more rotifers there were the
less cladoceran. (Tables 1 and 2)
- Recommendations for future studies would be to take more samples more
often and to measure the water clarity as it correlates to the amount of
plankton in Lake Wingra.
- The study that we have done on the seasonal changes of plankton in Lake
Wingra produced interesting results but there was no conclusive evidence on
how the weather affects the amount of plankton in Lake Wingra from the
research that we found.
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