Schampel, J. H. University of Minnesota, scha0306@tc.umn.edu
Schulz, K. H. University of Minnesota,
Sterner, R. W. University of Minnesota, stern007@maroon.tc.umn.edu

 
THE ROLE OF SMALL CONSUMERS IN THE PELAGIC FOOD WEB OF LAKE SUPERIOR'S WESTERN ARM
 
Despite Lake Superior's prominence as a freshwater body, its pelagic food web remains sparsely studied relative to many other lakes both large and small. Previous studies of the lake have focused on biomass pools and primary production, and indicate that they are dominated by the pico-planktonic (<10um) size fraction (Fahnenstiel et al. 1986, Fahnenstiel et al. 1998). However, little is known about the fluxes from these pools to higher trophic levels. Important questions on this front include: What size consumers are responsible for most of the grazing of phytoplankton and bacteria in Lake Superior? What size prey are contributing the most carbon (and nutrients) to higher trophic levels? What is the relative contribution of omnivory to these fluxes? To investigate these questions, experiments were run during 1996 and 1997 to assess grazing impacts of three consumer size classes (<10um, 10-80um, and >80um) on two prey size fractions (<10um, >10um). Results indicate that the smallest zooplankton (<10 um) are the principal consumers, grazing primarily on bacteria and small (<10 um) phytoplankton. Implications of these results for elemental-based (C, N, P) trophic transfer in Lake Superior's lower food web will be discussed.
 
Day: Thursday, Feb. 4
Time: 11:45 - 12:00pm
Location: Sweeney Center
 
Code: SS39TH1145S