SS4.05 Tribute to Thomas Frost
Date: Monday, June 10, 2002
Time: 2:00:00 PM
Location: Sidney
 
ArnottSE, Cooperative Freshwater Ecology Unit, Laurentian University, Sudbury, Canada, sarnott@nickel.laurentian.ca
Cooper, A, , Biology Dept, Laurentian University, Sudbury, Canada, alicooper26@hotmail.com
Alarie, Y, , Biology Dept, Laurentian University, Sudbury, Canada, yalarie@nickel.laurentian.ca
 
THE ROLE OF PREDACEOUS MACROINVERTEBRATES IN THE RECOVERY OF ZOOPLANKTON COMMUNITIES
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There is evidence that some ecological systems exhibit hysteresis in response to the removal of stressors. For example, legislated reductions in sulphur dioxide emissions have resulted in chemical recovery of lakes near Sudbury, Ontario, but biological recovery has been slow. Zooplankton communities in many chemically recovered lakes remain quite different from those in undisturbed lakes of similar pH. We hypothesized that in lakes with extirpated fish communities, macroinvertebrate predators flourish and therefore, control zooplankton community structure. We tested this hypothesis by conducting field surveys and mesocosm experiments. Aquatic macroinvertebrates were sampled in lakes with and without fish, along a pH recovery gradient. Macroinvertebrate communities were strongly influenced by the presence of fish, but did not vary according to the pH recovery gradient. Mesocosm experiments indicated that a predaceous beetle (Graphoderus liberus), found predominantly in fishless lakes, strongly influenced zooplankton community structure. These studies suggest that recovery of zooplankton communities from acidification may be influenced by macroinvertebrate predators and may therefore depend on the re-establishment of fish communities