The spatial distribution of the freshwater macroinvertebrate fauna of the River Ely, South Wales, in relation to pollutional discharges

Abstract

The spatial distribution patterns of the freshwater macroinvertebrate fauna of the River Ely catchment, South Wales, as determined by two extensive surveys, were examined in relation to changes in water quality, using cluster analysis and nodal analysis. An objective procedure was developed to identify robust species and site groupings from the several classifications arising from the use of different clustering methods. Species groupings so identified were found to be largely consistent with previous information on pollution tolerances. The major pollutants affecting species distributions in the Ely catchment were considered to be poorly treated sewage and the ammonia and suspended coal solids discharged from two coking plants. The investigation also demonstrated the ability of multivariate-data analytical techniques to identify causal relationships between changes in faunal composition and specific alterations in water quality.