Distribution patterns of free-living nematodes in differently degraded river reaches of the River Wien, Austria

Abstract

AbstractFree-living nematode communities were investigated at four morphologically different reaches along the River Wien, Austria. A near natural (NN) reach, two impounded reaches of different size (small and large: SI, LI) and a restored reach (RR) were sampled in autumn, winter, spring and summer (2004-2005). A total of 4144 individuals were counted and comprised 78 species. Nematodes of the impounded sites contributed least (5% at SI) and most (60% at LI) to the total fauna. Mean site abundances (ind./10 cm2) were 68, 27, 10 and 1 at RR, NN, LI and SI, respectively. Species diversity ranged from 1.59 at LI to 2.16 at RR. Bacterivorous nematodes dominated all sites (>50%); only algivorous Chromadoridae represented a high percentage contribution (46%) at LI. Based on this high portion, the maturity index (MI 1-5) was highest at this site (2.61). The MI indicated status of good water quality for the NN (2.5). The relatively low MI (2.10) and the high portion of cp1 Secernentea (14%) reflect the status of critical pollution at the restored site. The patterns of average taxonomic distinctness (ATD) did not optimally reflect habitat quality; a better descriptor of degraded river habitats seems to be the variation of taxonomic distinctness (VTD) in this study. In conclusion, the MI seems to be a better descriptor of pollution and the VTD of morphological degradation.