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Big Fish in a Small Pond: Ecology of Freshwater Habitats

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.

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Big Fish in a Small Pond: Ecology of Freshwater Habitats

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  1. 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

  2. ECOSYSTEM MODEL materials energy PRODUCERS Sun algae phytoplankton HERBIVORES Daphnia “water Fleas,” Cyclops NUTRIENT PREDATOR 1 POOL Catfish, Carp, Goldfish, Chaoborus PREDATOR 2 Kingfisher, Heron, Humans DECOMPOSERS

  3. “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.

  4. Exclusion Chambers Chamber 3: Catfish Chamber 2: Nutrients Chamber 4: Nutrients and Catfish Chamber 1: Control

  5. Adventures at Long Pond

  6. 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

  7. 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

  8. Dissolved Oxygen: NO PATTERNS!!

  9. Turbidity Controls

  10. Top-down vs. Bottom-up: Results Fig 1: Turbidity in Unit A Fig 2: Turbidity in Unit B

  11. Eutrophication: Methods • Controls with no added nutrients • Chambers with added nutrients • Chemical tests to measure turbidity and nutrient levels

  12. Eutrophication: Findings…

  13. 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

  14. 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

  15. Daphnia: Results Pond and nutrient solution did not support Daphnia reproduction as well as the pond water alone

  16. Let’s look at some culture dishes!

  17. Daphnia: Discussion • Result: Pond with nutrients did not support as much Daphnia as pond water alone. • Explanation: Nutrient enrichment in pond and nutrient dish hindered optimal Daphnia reproduction. • Result: Spring water dish could not maintain a stable Daphnia population • Explanation: It lacked the natural pond algae upon which the Daphnia feed.

  18. 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

  19. Bullhead Predation Results • Population counts for the pond on day one were high • All else were low; mostly a zero population count

  20. 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

  21. 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.

  22. Diagram of Pond

  23. Catfish: Results P values of significance test = 0.1157 (All fish) = 0.0975 (Catfish) α = .10

  24. 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

  25. 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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