Identifying key environmental variables structuring benthic fauna for establishing a biotic typology for Greek running waters

A central aspect of the Water Framework Directive 2000/60/EC addressed to Member Countries is to proceed to type-specific ecological assessment and classification by establishing typology systems. Sixty-four permanent stream sites distributed throughout mainland Greece and islands were assessed with macroinvertebrate indicators to evaluate their ecological quality. Local and catchment scale parameters were determined and recorded to obtain an integrated assessment of the main factors affecting stream integrity and macroinvertebrate communities. Twenty-three sites were classified as reference or good status in terms of biological, chemical and hydromorphological quality with the use of various metrics. Multivariate statistical techniques were performed (MDS, BIOENV, correlation analysis and PCA) to investigate the main environmental factors structuring benthic macroinvertebrate communities and to select candidate environmental variables for establishing a biotic typology for Hellenic rivers. The results revealed relatively distinct macroinvertebrate communities within defined abiotic zones of the country. Assemblages of macroinvertebrate fauna were most strongly associated to differences in geographical position, altitude, slope, catchment area, current velocity, conductivity and water temperature. In view of the lack of sufficient data at the country level on the three last variables and after considering cause-effect relationships between large scale variables and the latter, it has been demonstrated that a number of catchment scale variables could be used as robust surrogates.