SS3.18 Habitat Coupling in Lakes
Date: Thursday, June 13, 2002
Time: 9:45:00 AM
Location: Esquimalt
 
VadeboncoeurY, McGill University, Montreal, Canada, yvadeb@po-box.mcgill.ca
Kalff, J, , McGill University, Montreal, Canada, jkalff@bio1.lan.mcgill.ca
Rasmussen, J, , McGill University, Montreal, Canada, jrasmu@bio1.lan.mcgill.ca
 
RECIPROCAL RELATIONSHIPS BETWEEN BENTHIC AND PELAGIC PRIMARY PRODUCERS: ENERGETIC CONSEQUENCES FOR LITTORAL FISHES
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Most conceptual models of lake ecosystems depict phytoplankton as the energetic foundation of food webs, while littoral zones primarily provide structural complexity. We assessed the energetic importance of benthic primary producers to fish in a large oligotrophic lake. Periphyton and phytoplankton production were negatively correlated along a phytoplankton gradient. Stable isotope analysis revealed that, except for mussels, benthic invertebrate production was derived from carbon fixed by periphyton. Young of year fish relied on phytoplankton derived carbon, but all adult littoral piscivores relied predominantly on carbon fixed by epiphytic and epipelic algae, not phytoplankton. Yellow perch (Perca flavescens) densities were positively correlated with macrophyte cover and periphyton production. Growth rates of perch (1+ and older) were positively correlated with the extent to which periphyton-based food chains were exploited. Thus, when eutrophication suppresses benthic primary producers, it not only alters littoral habitats, it erodes the energetic base of food chains that are heavily exploited by piscivores.