Scaling the trophic status of the Aegean Sea, eastern Mediterranean

Data on chl-a and primary production were recorded from the northern to the southern open waters and from inshore to offshore waters of the Aegean Sea. The data were analysed statistically and their levels were scaled and characterised on the basis of probabilistic parameters. The limits of average chlorophyll concentrations and productivity in open oligotrophic waters were less than those in the offshore mesotrophic and these were less than in inshore eutrophic waters. According to this scaling, the categories 'open oligotrophic'  <  'offshore mesotrophic'  <  'inshore eutrophic' waters were defined for chl-a as 0.5 < (0.5 - 1.0) < 1.0 mg m− 3, and for primary production as 1.5 < (1.5 - 3.0) < 3.0 mg C m− 3 h− 1. The comparison of the mean depth of the euphotic zone also displayed a characteristic gradient from oligotrophic open waters (90-129 m) to mesotrophic offshore (35 m) and eutrophic inshore (7 m) waters. Eutrophication is a major problem in most of the European regional seas including the Mediterranean and the Black Sea. The classification of the trophic status of seawater is important because it is central to ecological studies of eutrophication and its practical role as an indicator of water quality.