CS39A Zooplankton - Feeding, Reproduction, Growth and Molecular Diversity
Date: Tuesday, June 11, 2002
Location: Poster Session - VCC
GrossDH, Utah State University, Logan, USA, donovan@cc.usu.edu
Luecke, C, , Utah State University, Logan, USA, luecke@cnr.usu.edu
Phytoplankton Nutrient-limitation In Arctic Lakes With And Without Fish
Nutrient-limitation of phytoplankton growth did not vary among four arctic lakes with contrasting food webs. Nutrient-addition bioassays were conducted in-situ in two lakes with fish and two lakes without fish, with characteristically different zooplankton communities, twice throughout the summer to test the effect of herbivore nutrient-recycling on the nutrient-limitation of phytoplankton. Nutrients were added in a 13.4-to-1 molar nitrogen-to-phosphorus ratio. In all cases, nitrogen alone stimulated more phytoplankton growth than did phosphorus alone (64 to 137% more chlorophyll a). Analysis of the associated zooplankton communities indicates cladoceran dominance (biomass), including Daphnia and Bosmina, in fishless lakes early in the summer and copepod dominance later in the season. Lakes with fish exhibited zooplankton communities dominated by copepods (biomass) throughout the season. These data suggest that natural abundances of herbivores have little effect on the nutrient-limitation of associated phytoplankton in small freshwater lakes.