PARENT SESSION
Oral Session #56: Aquatic Ecology: Plankton. Presiding: N. Hairston.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas I.
Keystone conduits for metal trophic transfer in lakes.
Folt, Carol1, Chen, Celia1, Pickhardt, Paul1, 1
ABSTRACT- This study was designed to compare several common zooplankton taxa for their potential to act as keystone conduits for metal trophic transfer. We define keystone conduits as species that are particularly important in determining whether metals will be transferred more or less efficiently to top predators. To investigate the degree to which variation in the bioaccumulation and biomagnification of metals (Hg, As, Cd and Zn) in lakes is dependent on keystone conduit species, we measured metals in specific zooplankton taxonomic groups (cladocerans, calanoid and cyclopoid copepods) from 14 survey lakes. We found strong evidence for the taxonomic specificity of metal trophic transfer to fish. Cladocerans, which are an especially important food for planktivorous fish, carry higher burdens of certain metals (Hg and As, in particular) than copepods in the same lakes. We also found an increase in the uptake of methyl-Hg and inorganic Hg by cladocerans relative to copepods in controlled mesocosm experiments. This difference has important implications for trophic transfer, and suggests that in lakes where the food web is dominated by large cladocerans the transfer of metal to fish is likely to be greater than in lakes dominated by small calanoids and cyclopoids. Evidence to support this contention from the field will also be presented.
KEY WORDS: foodwebs, metals, keystone, zooplankton