Aquatic Sciences Meeting, Albuquerque 2001

CS34 Trophic Dynamics

Date: Friday, February 16, 2001, Time: 10:45:00 AM

Location: Mesilla

Harper, S, J, Miami University, Oxford, USA, harpersj@muohio.edu

Vanni, M, J, Miami University, Oxford, USA, vannimj@muohio.edu

RESISTANCE AND RESILIENCE OF FOOD WEBS TO NUTRIENT PERTURBATIONS: THE ROLE OF OMNIVOROUS FISH

Theory suggests that omnivory can confer stability to food webs through the addition of weak- to moderate-strength trophic interactions. Additionally, omnivorous fish that feed extensively on sediment may confer stability by transporting a large, steady supply of nutrients from the sediment layer to the grazer-based food web. We conducted studies to test the hypothesis that omnivorous fish increase the resistance and resilience of aquatic food webs to perturbations. We assembled experimental food webs to resemble those found in reservoirs, systems that routinely receive large pulses of nutrients following storms. In 12 ponds, we established food webs with phytoplankton, zooplankton, planktivorous bluegill, and various densities (none, low, moderate, and high) of omnivorous gizzard shad, Dorosoma cepedianum. Following a 6-wk pre-manipulation period, we perturbed ponds with a nutrient pulse over a 2-d period and then monitored responses of food webs over a 5-wk post-manipulation period. Results supported our hypothesis as food webs with omnivorous fish showed increased resistance and resilience to the perturbation. Additional studies are required to discern the underlying mechanism by which omnivorous fish confer stability to food webs.

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Aquatic Sciences Meeting, Albuquerque 2001

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