Distribution of benthic macroinvertebrate communities and assessment of water quality in a small UK river catchment

Communities of benthic macroinvertebrates obtained from a river catchment impacted by point source pollution were investigated from March 2013 to April 2014. The main purpose of this study was to describe the taxon richness of benthic macroinvertebrate communities obtained at upstream and downstream of a wastewater treatment works and combined sewer overflows, assess water quality and to determine major physicochemical variables that affect the distribution and richness of benthic macroinvertebrate communities. The biotic index Whalley Hawkes, Paisley and Trigg revealed distinction between the sites upstream of the wastewater treatment works from the downstream sites. Between and within sampling locations, the dominance of certain taxonomic groups was recorded including Oligochaete, Baetidae and Chironomidae. Predominant in the river were insects which constituted 72% of the overall benthic invertebrate communities followed by Oligochaeta (28%). Distribution of benthic macroinvertebrate communities was not associated with sewage variables but related more with altitude, catchment area, slope and discharge. Altitudes range from 31 to 140 m. The sites at higher altitude had better quality compared to the lower sites and therefore suggests that altitude could provide a spatial proxy for anticipated future ecological changes in the river over time. Classification of the river based on the European Union’s Water Framework Directive indicated that the river had moderate ecological status.