Effects of nutrient enrichment on the trophic structure and species composition of freshwater nematodes—a microcosm study

Abstract

AbstractWe explored changes in trophic structure and species composition of freshwater nematodes in response to nutrient enrichment in microcosms for 16 mo. Succession of functional groups differed significantly among the 5 nutrient treatments, which ranged from oligotrophic to polytrophic conditions, in the 2nd half of the experiment. Differences among nutrient levels were most important for representatives of lower trophic levels, such as bacterial and algal feeders, whereas suction feeders and predators remained relatively unaffected. In contrast to our expectations, density and biomass of bacterial and algal feeders increased in the nutrient-poor treatments because of the presence of a high fraction of edible unicellular green algae and diatoms, whereas large standing stocks of inedible macrophytes developed in the highly nutrient-enriched treatments. Nematode assemblages in microcosms with intermediate or high nutrient levels were characterized by a large proportion of omnivores and predators, respec...