Assessment of pressures and impacts on surface water bodies of the Mediterranean. Case study: Pamvotis Lake, Greece

Abstract

The aim of the study presented in this article is to assess the ecological status of a surface water body in the Mediterranean using the methodological approach of Driver-Pressure-State-Impact-Response. Based on this approach for the case study analyzed (Pamvotis Lake, Greece), it is concluded that the main drivers, which lead to pressures in the study area are: intensive agricultural activities, alteration of hydrological regime, contamination from point sources and changes in the land-use and fish stocking. The ecological status is assessed by analysing data series of physical, chemical and biological elements that are available from early '80s. Findings suggest elevated nutrient concentrations sufficient for maintaining eutrophic conditions while their seasonal variability is mostly driven by factors as water level fluctuation, catchment runoff and in-lake biological processes. Subsequently, concerning biotic factors, the poor biodiversity mainly represented by the dominance of the most tolerant species, confirm the previous profile. Since, reference conditions have only recently been established in Greece, the ECOFRAME scheme and the guidelines proposed by the "Intercalibration Group for Mediterranean Lakes" were applied. In terms of the above elements; the water quality status could be characterized as "High", "High to Good" and "High to Bad", respectively, whereas the overall ecological status tends to shift in poor conditions. Finally, the major response actions needed should be in the direction of reduced application of fertilizers and chemicals in the cultivated land of the catchment, removal of the point-contamination sources from the catchment, appropriate land-use management and biomanipulation.