SS4.07 Lipids/Fatty Acids in Ecological Research
Date: Tuesday, June 11, 2002
Time: 11:00:00 AM
Location: Saanich
 
BrettMT, University of Washington, Seattle, USA, mtbrett@u.washington.edu
Danielsdottir, M, , University of Washington, Seattle, USA, martag@u.washington.edu
 
Algal food quality control of the strength of aquatic food web interactions
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We developed a dynamic model of nutrient, phytoplankton, zooplankton and fish interactions in a hypothetical temperate polymictic lake, in order the test the potential impact algal food quality and nutrient availability on food web biomass distribution. This model suggests algal food quality and zooplanktivory interact to determine zooplankton biomass. When algal food quality is low, moderate zooplanktivory will drive zooplankton to extinction. When algal food quality is high, zooplankton can withstand intense zooplanktivory. Once the zooplankton overcomes the risk of extinction due to poor food quality and/or intense zooplanktivory, it is able to buildup a large biomass and suppress phytoplankton. Algal biomass is strongly regulated by both nutrient availability and zooplankton biomass. Algal-zooplankton interactions become unstable at high nutrient concentrations and especially when algal food quality is high. When algal food quality is high, algal biomass (relative to nutrient availability) is low, and the zooplankton to phytoplankton biomass and phytoplankton community production to biomass ratios are high. Our results suggest a bottom up factor (i.e. algal food quality) will determine the strength of top down control of algal biomass.