Freshwater mussels are important components of river biodiversity and are highly sensitive to pollution of river ecosystems. As a result of historical declines in river water quality in the UK, freshwater mussel numbers have decreased significantly. There is currently only one population that is considered to be secure in England, located on the River Ehen in Cumbria. This research project will examine the factors behind recent pressure on this population of freshwater mussels. The research at Lancaster focuses on understanding the factors which control the abundance and composition of the algal community living on the bed of the River Ehen. The proliferation of this benthic algal community, driven by the hydrological and water quality conditions that govern the benthic community, is hypothesised to be one possible cause of pressure on the freshwater mussel population in the River Ehen. This project involves collaboration with leading algal ecologist Dr Martyn Kelly and with the Environment Agency and United Utilities.