Defining the coastal water quality in Estonia based on benthic invertebrate communities

Abstract

The European Union Water Framework Directive requires that all member states assess the status of their coastal areas and develop or use existing classification systems to support future monitoring. To set the quality assessment system for the Estonian coastal sea, the composition of modern zoobenthic communities was compared to the communities from the 1950s?1960s. Sensitivity values of benthic taxa were determined, and the macrozoobenthic community index ZKI and boundaries for the classification system were developed. The ZKI index was further validated against nutrient loads and the spatial location relative to pressure, represented by the Baltic Sea Pressure Index (BSPI). High variability in Ecological Quality Ratio assessment results was found for both ZKI and brackish water benthic index (BBI) based assessments. However, in the study area, ZKI assessments fluctuated to a smaller extent and displayed a better correlation with the BSPI than the BBI assessments.