COMPARISON OF MEIOBENTHIC CRUSTACEAN COMMUNITY STRUCTURE ACROSS FRESH-WATER ACIDIFICATION GRADIENTS

Analytical procedures that use the structure of natural communities to detect anthropogenic disturbance in marine systems were applied to fr eshwater data for the first time. Species data for meiobenthic crustac eans from streams in two regions of Britain affected by acidification (southern England and mid-Wales) were ordinated using non-metric Multi dimensional Scaling (MDS) to determine if an influence from pH could b e detected either: i) at taxonomic levels higher than species (genus a nd family); or ii) across regions. Relationships between community str ucture, pH and other environmental variables were investigated using t he BIOENV procedure. In English streams, pH had a clear influence on c ommunity structure that was most clearly detected at species level but was still evident after data were aggregated to genus and family. In contrast, pH had no influence on communities in the Welsh streams, but there was a significant difference in community structure at all taxo nomic levels between streams in conifer plantations and those in moorl and. There was also a significant difference in community structure be tween regions, which tended to override any influence from pH, althoug h, at family level, there was a gradient from acidic sites in southern England and those draining conifer plantations in Wales to less distu rbed sites in both regions. This study suggests that meiobenthic commu nities can be used for the detection of pollution gradients in freshwa ters, but that this approach may only be of use where regional differe nces in stream physicochemistry are minimal.