Community Response to Cumulative Toxic Impact: Effects of Acclimation on Zinc Tolerance of Aufwuchs

Abstract

Aufwuchs communities were developed on artificial substrates in a local pond. Second-generation communities were developed on identical substrates in laboratory systems receiving three levels of zinc (Zn): background, 73, and 172 μg∙L−1. After 21 d, second-generation communities were exposed to five concentrations of Zn ranging from background to 10 078 μg∙L−1 for 48 h. Protozoan communities developed under Zn stress were initially less rich taxonomically but subsequently lost fewer species in response to acute Zn exposures. Richness remaining after exposure to high Zn levels [Formula: see text] was similar for all groups. Taxonomic composition changed less in acclimated communities than in the control in response to secondary stress. Gross primary productivity was less impaired by secondary stress in communities acclimated to Zn. Community respiration, algal biomass, total biomass, respiration to biomass ratios, and ratios of soluble to total reactive phosphates did not differ in response to secondary stress. In general, communities developed under Zn stress were initially impaired but changed less in response to additional stress relative to their initial state.