The impact of short-term exposure to UV-B radiation on zooplankton communities in north temperate lakes

We exposed natural zooplankton communities to in situ levels of sunlight for 3 days at different depths in two north temperate lakes: one oligotrophic and one eutrophic. Natural fluxes of UV-B radiation (280–320 nm) were manipulated with cutoff filters (Mylar®). There was substantial mortality in some of the zooplankton exposed to UV-B in the oligotrophic lake, but not in the eutrophic lake. Reproduction of Diaptomus was suppressed by UV-B down to 6 m in the oligotrophic lake. These data suggest that natural levels of UV-B radiation in the oligotrophic lake may prevent some species of zooplankton from continuously exploiting the warm surface waters during summer stratification. In the more eutrophic lake, UV-B is a less important constraint in the vertical distribution of zooplankton. These differences in the responses of zooplankton to natural UV-B radiation in lakes may alter their ecological interactions with food resources, predators and other environmental variables in the water column.