Kemp, W. M. UMCES/HPL, kemp@hpl.umces.edu
Brooks, M. M. Western Maryland College, mbrooks@hpl.umces.edu
Hood, R. R. UMCES/HPL, raleigh@hpl.umces.edu

 
PRODUCTIVITY, VARIABILITY AND TROPHIC TRANSFER EFFICIENCY IN PELAGIC FOOD WEBS
 
A theoretical study was undertaken to explore how the efficiency of organic matter transfer from lower to higher trophic levels depends on the mean and variability in levels of primary production in pelagic food webs. Heuristic numerical models were developed to address this question at two levels of ecological organization: the organism and the ecosystem. At the organism level, a Holling Type III feeding function was used to simulate interactions of a consumer with its food resource at different resource levels and variabilities. With increases in relative variance of food availability, efficiency increased under conditions of sparse food and decreased with abundant food, while efficiency was independent of variance a intermediate food concentrations. At the ecosystem level, a simple five-compartment food web model was used to explore how variability in nutrient supply and primary productivity impact transfer efficiency due to changes in food web structure. Trophic efficiency (zooplankton growth/GPP) was maximal at intermediate nutrient and primary productivity levels, with longer trophic pathways dominating under low nutrients and high nutrients leading to saturation of zooplankton feeding. In contrast, trophic efficiency was enhanced by variable nutrients only under oligotrophic conditions. Variance imparted to nutrient resources was propagated through the food web to zooplankton more effectively under oligotrophic than eutrophic conditions. These results suggest that food web efficiencies are more dependent on level of resource availability (
 
Day: Thursday, Feb. 4
Time: 10:30 - 10:45am
Location: Hilton of Santa Fe
 
Code: SS04TH1030H