Cross-taxon responses to elevated nutrients in European streams and lakes

Abstract

Few studies have compared the response of different taxonomic groups to environmental stress across aquatic ecosystems. We regressed assemblage structure of fish, invertebrates, macrophytes, phytoplankton and benthic diatoms to total phosphorus concentration, after removing the effect of ecosystem size (stream order, lake surface area), using data from 66 streams and 45 lakes across Europe. In streams, the structure of benthic diatom assemblages, measured by nonmetric multidimensional scaling, showed the strongest correlation to elevated nutrient concentrations (adj. R2 = 0.495), followed by benthic invertebrates (0.376), fish (0.181) and macrophytes (0.153). For lakes, the patterns were less clear: fish (0.155), macrophytes (0.146) and phytoplankton (0.132). Cross-system comparison showed that stream assemblages were responding more strongly to nutrient concentrations than lake assemblages. Moreover, our results lend some support to the conjecture that response signatures are related to trophic level, with primary producers (benthic diatoms) responding more strongly than consumers (invertebrates, fish). Knowledge of differences in responses among taxonomic groups and between habitats to disturbance can be used to design more cost-effective monitoring programs.