Invertebrate communities in soft sediments along a pollution gradient in a Mediterranean river (Llobregat, NE Spain)

The Llobregat is a highly-perturbed Mediterranean river affected by a wide range of pollutants. High concentrations of soluble reactive phosphorus and chloride are the clearest indicators of pollution in this basin. Seven sites in the mid and lower Llobregat basin were sampled in June 2005 to examine the invertebrate community inhabiting the soft sediments along this pollution gradient. Spatial distribution analysis revealed differences in chemical parameters, and in the composition and biomass of the invertebrate community. Most of the taxa found are opportunistic and reflect low or unacceptable biological water quality. Nevertheless, changes in their abundance, biomass and diversity reflect the longitudinal pollution gradient in the river.