Stoicescu S.-T., Lips U., Lips I.
The Baltic Sea is a sea basin affected by human-induced eutrophication. As required by the Baltic Sea Action Plan and Marine Strategy Framework Directive, the status of the marine areas is assessed based on indicators showing whether the good environmental status (GES) is achieved or not. The main result of the present work is that based on the national monitoring data from 2011-2016 and used nutrients, direct effects and indirect effects indicators, the entire Estonian marine area is affected by eutrophication. The overall eutrophication status is mostly defined by nutrient concentrations in the water or direct effects of eutrophication (chlorophyll-a, phytoplankton biomass, and water transparency). The non-GES result in the shallow Moonsund area is mostly determined by total phosphorus (TP) suggesting that thresholdvalues for TP should be studied in more detail. The assessment results derived based on the proposed dissolved inorganic nutrients thresholds for the Estonian coastal waters agree well with the adjacent offshore assessment results. According to the suggested confidence evaluation scheme, the overall assessment result has mostly intermediate confidence, but high confidence in the open Gulf of Finland and coastal water bodies covered with yearly monitoring. Intermediate confidence in status assessment and the noticed high variability in the assessment results in the basins with monitoring data from only one year, point to the need for an increase of monitoring frequency there.