Masterson, C. F.. Michigan State University, master13@pilot.msu.edu
Skubinna, J. F.. Michigan State University, skubinna@pilot.msu.edu
Ostrom, N. E.. Michigan State University, ostromn@pilot.msu.edu
Ostrom, P. H.. Michigan State University, ostrom@pilot.msu.edu
Hall, D. J.. Michigan State University, eebb@pilot.msu.edu
Coon, . G.. Michigan State University, coontg@pilot.msu.edu

 
USING STABLE ISOTOPES TO INVESTIGATE SEASONAL VARIATION IN THE FOOD WEB OF GRAND TRAVERSE BAY, LAKE MICHIGAN
 
Seasonal variations in the trophic structure of Grand Traverse Bay were investigated using stable isotope data. Food web components were collected from April to September in 1997 and 1998. In 1997, nitrogen isotope values declined seasonally in seston, zooplankton, amphipods, and mysids by 1.8 per mil or more. The most striking declines were observed among bulk zooplankton (8.4 per mil) and seston (4.2 per mil). The difference in nitrogen isotope values between zooplankton and seston decreased from April (7.6 per mil) to September (3.3 per mil), which may indicate a reduction in the average trophic level of zooplankton. This is likely a result of seasonal variations in feeding habits that could be associated with changes in community structure. Alewife was the only fish species to exhibit the seasonal isotopic decline, and appeared to have a close association with herbivorous zooplankton. Nitrogen and carbon isotope data were used in combination with stomach contents to investigate the relative importance of seston, sinking particles and sedimentary organic matter to higher trophic levels. This is particularly relevant in assessing exposure routes by which organic contaminants bioaccumulate in fish.
 
Day: Wednesday, Feb. 3
Time: 11:15 - 11:30am
Location: Eldorado Hotel
 
Code: SS32WE1115E