Big Fish in a Small Pond: Ecology of Freshwater Habitats Project in Environmental Biology Mr. Michael T. Roche Matt Singer Dan Currie, Mario De Franco, Laura Fong, Rashi Grewal, Andrew Herman, Jane Hur, Linda Karas, Rachel Kolesnikov-Lindsey, Lea Pope, Max Weidmann ECOSYSTEM MODEL materials energy Sun PRODUCERS algae phytoplankton HERBIVORES Daphnia water
Fleas, Cyclops NUTRIENT POOL PREDATOR 1 Catfish, Carp, Goldfish, Chaoborus PREDATOR 2 DECOMPOSERS Kingfisher, Heron, Humans Top-down vs. Bottom-up Theories Top-down theory: Predator population is the main influence on lower trophic levels. Bottom-up theory:
Nutrient levels are the main influence on producer population. Top Down Manipulation Bottom Up Manipulation Carnivores Upper level predator Exclude Catfish Primary predator Herbivores Cladocera Copepods
Up+ Up+ Nutrients & Catfish 4 added ? ? Open Pond Autotrophs Used as control Added Stim x2 dir
Added None added Exclusion Chambers Chamber 2: Nutrients Chamber 1: Control Chamber 3: Catfish Chamber 4: Nutrients and
Catfish Long Pond X5 X4 X6 X3 Adventures at Long Pond Key: vegetation fallen logs X2 fish trap location X1 N
X exclusion chambers Our Experiments and Hypotheses Top-down vs. Bottom-up: The two forces together would create a more stable environment than they would independently Eutrophication: Increased nutrients (N, P, K) cause higher producer levels Bullhead Catfish Predation: The size of the bullhead catfish does not affect their predation on plankton
Daphnia: Pond water enriched with nutrients will support the highest Daphnia population White vs. Rye: Catfish will prefer rye bread over white bread Top-down vs. Bottom-up: How was it done? Collected water samples from both units (8 chambers) and pond itself Tested water samples for dissolved oxygen and turbidity levels Studied results to estimate relative phytoplankton populations Dissolved Oxygen: NO
Thursday, 8/ 05/ 04 Monday, 8/ 09/ 04 Fig 1: Turbidity in Unit A B3 Monday, 8/ 02/ 04 Thursday, 8/ 05/ 04 Monday, 8/ 09/ 04 Fig 2: Turbidity in Unit B Eutrophication: Methods Controls with no added nutrients Chambers with added nutrients Chemical tests to measure turbidity and nutrient levels Eutrophication: Findings 6 PPM
Thursday, 8/05/04 Monday, 8/09/04 Eutrophication: Discussion Hypothesis is supported Fertilizer leaves little lasting impact Nitrogen cycles through ecosystem in all chambers Phosphorus accumulates in nutrient enriched chambers Catfish left large impacts on nutrient and turbidity levels Daphnia: Methods Three culture dishes with egg yolk: 1. Spring water 2. Pond water
3. Pond water enriched with nutrients Add five Daphnia to each dish Perform visual counts every two days Determine population density Population Density (#/100mL) Daphnia: Results 700 600 500 400
300 200 100 0 Spring Pond Pond + nut. 0 2 4 6 Day Pond and nutrient solution did not support Daphnia reproduction as well as the pond water alone Lets look at some culture dishes!
Daphnia: Discussion Result: Explanation: Result: Explanation: Pond with nutrients did not support as much Daphnia as pond water alone. Nutrient enrichment in pond and nutrient dish hindered optimal Daphnia reproduction.
Spring water dish could not maintain a stable Daphnia population It lacked the natural pond algae upon which the Daphnia feed. Bullhead Predation Methods Chamber A3: Four small fish Chamber A4: Four large fish with nutrients Chamber B3: Four large fish Chamber B4: Four small fish with nutrients
50mL from vertical tows added to 50mL ethanol Cyclops and Daphnia populations counted by 10 mL samples Bullhead Predation Results Population counts for the pond on day one were high All else were low; mostly a zero population count Bullhead Predation Discussion Population counts were low for both small and large fish; data is inconclusive Possibly due to the way chambers were stocked Three fish died in A4 four days into the study
Catfish: Methods Traps distributed around pond Each trap baited with either white or rye bread Thirty minute trials Null Hypothesis: There will be no difference in the effectiveness of the type of bread used as bait. Alternate Hypothesis: There will be a difference. Diagram of Pond Long Pond X5 X4 X6 X3
Key: vegetation fallen logs X2 fish trap location X1 N X exclusion chambers Catfish: Results Number of Catfish v. Type of Bread 20 18 16 14 12
10 8 6 4 2 0 Number of Catfish Number of Fish Number of Fish v. Type of Bread rye white 20 18 16 14 12 10
8 6 4 2 0 rye Type of Bread white Type of Bread P values of significance test = 0.1157 (All fish) = 0.0975 (Catfish) = .10 Catfish: Discussion Catfish, goldfish, and carp were collected in the traps The fish preferred rye bread statistically
significant for catfish If more trials conducted, results may have been more significant Conclusions and Suggestions for Further Study Top-down vs. Bottom-up: The environments experiencing equal forces top down and bottom up appear most stable Eutrophication: Future studies should limit enrichment chambers to one nutrient Bullhead Catfish Predation: Data inconclusive Daphnia: Both Pond and Nutrient-enriched chambers were capable of sustaining populations. White vs. Rye: Rye bread functions as a more effective bait.
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