PARENT SESSION
Oral Session #33: Climate Change. Presiding: A. Peterson.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Hall of Ideas E.
Global warming and zooplankton communities in alpine ponds of the Canadian Rocky Mountains: A greenhouse-warming experiment.
VINEBROOKE, ROLF1, COBB, TYLER1, STRECKER, ANGELA1, 1
ABSTRACT- Alpine and polar ecosystems are expected to experience the most pronounced impacts of global warming. We hypothesized that a temperature increase of 3°C would enhance zooplankton production and alter community composition by stimulating rapidly reproducing species in alpine ponds. The hypothesis was tested using three blocks of four experimental mesocosms (1000-L capacity) located next to permanent alpine (2400 m above sea level) ponds in Banff National Park, Canada. Each block received unfiltered water and sediments from an adjacent host pond following ice-out in June 2000. A warming treatment (control versus 3°C) was achieved by controlling ventilation of greenhouse canopies that were placed over the mescosms. After two months, warmer temperatures had significantly altered zooplankton species composition by favouring rotifers (Keratella cochlearis) and small cladocerans (Ceriodaphnia recticulata) over larger cladocerans and copepods. Warmed mesocosms also contained significantly more edible phytoplankton biomass, suggesting that warming had both direct and indirect positive effects on small, fast-growing zooplankton species. In contrast, community-level response variables (total biomass, species richness) were not significantly affected by elevated temperature. We suggest that the earliest responses of alpine aquatic ecosystems to global warming are changes in species composition involving increased abundance of rapidly reproducing species with wide dispersal powers.
KEY WORDS: global warming, alpine ecosystems, zooplankton, species composition