Zooplankton response to climate warming: a mesocosm experiment at contrasting temperatures and nutrient levels

Abstract

Zooplankton community response to the combined effects of nutrients and fish (hereafter N + F) at contrasting temperatures was studied in a long-term experiment conducted in 24 shallow lake mesocosms with low and high nutrient levels. We found a positive effect of N + F on zooplankton biomass, chlorophyll-a and turbidity. In contrast, zooplankton species and size diversity decreased with added N + F, as did submerged macrophyte plant volume inhabited (PVI). The community composition of zooplankton in high N + F mesocosms was related to chlorophyll-a and turbidity and to macrophyte PVI in the low N + F mesocosms. Macrophytes can protect zooplankton from fish predation. Compared to N + F effects, temperature appeared to have little effect on the zooplankton community. Yet analysis of community heterogeneity among treatments indicated a significant temperature effect at high N + F levels. The results indicate an indirect temperature effect at high N + F levels that can be attributed to temperature-dependent variation in fish density and/or chlorophyll-a concentration.