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.


Meris chlorophyll a concentration (percentile 90) in 2011 (Credit: MarCoast project)

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.


Phaeocystis globosa. Left: colonies; right: foam produced by the degradation of colonies (credit: V.Rousseau).

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.


Lancelot, C., Rousseau, V. and Gypens, N., 2009. Ecologically based indicators for Phaeocystis disturbance in eutrophied Belgian coastal waters (Southern North Sea) based on field observations and ecological modeling. Journal of Sea research, 61: 44-49.

Spatharis, S. and Tsirtsis, G., 2010. Ecological quality scales based on phytoplankton for the implementation of water framework directive in the Eastern Mediterranean. Ecological Indicators, 10: 840-847.