The freshwater biota of British agricultural landscapes and their sensitivity to pesticides

This study analysed information from national and regional datasets gathered in Great Britain describing the occurrence of aquatic macroinvertebrates and macrophytes in ponds, ditches, streams, rivers and lakes, across 12 agricultural landscape classes and a 13th class comprising non-agricultural land. The study found major differences in the composition of the invertebrate faunas of running and still water. River and stream assemblages had a relatively high proportion of species (20–40%) in groups believed to be sensitive to pesticides (mayflies, stoneflies, amphipod crustaceans). The proportion of these taxa also varied across the landscape with greater numbers of pesticide-sensitive species present in streams in more acid landscape classes. Ponds, in contrast, were dominated by water beetles and water bugs and supported fewer sensitive taxa (ca. 5% of the species present). The proportion of the fauna made up by these two taxonomic groups in ponds varied little between landscape classes. Ditches were intermediate between ponds and streams in both taxonomic composition and their variability across landscape class. Invertebrate species richness and rarity values were highest in rivers and ponds with fewer species in streams and ditches. Ponds typically supported more uncommon invertebrate species than other waterbody types. Plant assemblage data showed that, except for lakes, wetland landscape types (fenlands and valleys) were generally richer in species, with more uncommon taxa, than other landscapes. Ditch floras were often outstanding in these areas. The study findings have applications and implications in areas such as the development of environmentally valid mesocosm studies and for the creation of realistic scenarios in probabilistic risk assessment.