SS1.05 How Will Aquatic Ecosystems Respond to Climate Change?
Date: Tuesday, June 11, 2002
Time: 10:15:00 AM
Location: Oak Bay
 
VinebrookeRD, Freshwater Biodiversity Laboratory, University of Regina, Regina, Canada, rolf.vinebrooke@uregina.ca
Strecker, A, L, Freshwater Biodiversity Laboratory, University of Regina, Regina, Canada, 
Cobb, T, P, Freshwater Biodiversity Laboratory, University of Regina, Regina, Canada, 
Graham, M, D, Department of Biology, University of Regina, Regina, Canada, 
 
COUPLING OF ZOOPLANKTON AND PHYTOPLANKTON RESPONSES TO EXPERIMENTAL GREENHOUSE WARMING OF ALPINE PONDS
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Alpine ecosystems are expected to experience pronounced impacts of climate warming. We hypothesized that an increase of 4 degrees Celsius in alpine ponds would enhance plankton abundance and alter species composition by stimulating fast-growing, small species. The hypothesis was tested experimentally using three blocks of four 1000-L mesocosms that were established by alpine ponds following ice-out. A warming treatment was achieved by controlling the ventilation of greenhouse canopies placed over each mesocosm. Warming had a time-dependent negative effect on the total biomass of cladocerans, but not copepods. Also, warming shifted zooplankton size structure towards smaller species of rotifers. In warmed mesocosms, declines in cladoceran biomass and species size structure followed a decline in edible phytoplankton abundance and a compensatory shift towards inedible filamentous green algae. Cubitainers experiments revealed that warming had increased grazing by cladocerans. Therefore, warming probably caused daphnids to overexploit their food source, and experience increased metabolic costs relative to smaller rotifers and omnivorous copepods. Our findings suggest that climate warming reduces the reliability of food availability and water quality in climatically-sensitive aquatic ecosystems by destabilizing grazing dynamics.