PARENT SESSION
Oral Session #11: Aquatic Ecology: Conservation, Plankton, Invertebrates.
Presiding: C. Cooper
Monday, August 5. 8:00 AM to 11:30 AM. Palo Verde Room, Radisson.

Linking ecosystem processes to community structure: Lessons on compensatory mechanisms in arctic lakes.

Luecke, Chris^*,1, Burkart, Greta¹, ¹ Utah State University, Logan, Utah

ABSTRACT- The structure of zooplankton assemblages in arctic lakes varies with water depth. Shallow lakes freeze solid during winter and are not generally inhabited by fish. These lakes are dominated by high biomass of large-bodied zooplankton. Deeper lakes contain fish and are dominated by low biomasses of small bodies zooplankton. We examined ecosystem processes of production, herbivory, and nutrient cycling in both types of lakes. Results indicated that although zooplankton biomass was five-fold higher in fishless lakes compared to lakes with fish, rates of secondary production and herbivory were only twice as high. Simulation modeling indicated that increased per capita rates of feeding and production in lakes with fish explained 60% of these discrepancies between community biomass and ecosystem process. Our results suggest that the remaining 40% of the observed variation was due to species effects. These types of compensatory mechanisms reduce ecosystem effects resulting from changes in species composition.

KEY WORDS: ecosystem process, community structure, zooplankton , arctic lakes