Indicators of undesirable marine eutrophication

Most existing eutrophication indicators are based on Chlorophyll a (Chl a), a parameter integrative of phytoplankton biomass, in combination with physico-chemical indicators.

However Chl a as such is often not sufficient to properly assess the negative effect of changing nutrient loads on the ecosystem structure and function. For instance regional indicators based on either the combination of phytoplankton biomass and diversity metrics (e.g. Spatharis and Tsirtis 2010) or an undesirable cell threshold (e.g. Phaeocystis; Lancelot et al., 2009) have been suggested for respectively the Mediterranean Sea and Southern North Sea ecosystems.

Overall there is an urgent need for identifying ecologically-based indicators for scaling eutrophication problems in regional seas and identifying ecologically-sound targets. In addition, as local ecosystems extend over countries and water masses continuously cross national boundaries, an integrated and consistent EU policy would require an homogenization of the official thresholds defining the Good Environmental Status (GES) across the NEA.