HELCOM indicators of eutrophication: are the "environmental objectives" achievable for the Gulf of Finland?

The environmental status of the Gulf of Finland water environment was analyzed on the basis of data of Russian State Hydrometeorological University complemented by data of international monitoring. Also, the chlorophyll a data from satellite observations were used. Observed values of eutrophication indicators (such as concentrations of winter nutrients, chlorophyll a, bottom oxygen content, Secchi depth) in the Gulf of Finland are exceeding the HELCOM target values most of the times through the period of seasonal observations in 2014. However, the variability patterns are different for the two parts of the Gulf of Finland (Western and Eastern) reflecting the natural differences in morphometric structure and formation of their hydrochemical and hydrobiological regime. In general the western part of the Gulf is close to the "Good Environmental Status (GES)" defined in the Baltic Sea Action Plan (except for indicator: bottom oxygen content). However, in the Eastern part of the Gulf there are permanent elevated levels of nutrients (in last several years in particular), lack of oxygen, and very low transparency as compared to HELCOM target values. Therefore, the achievement of GES for this part of the Gulf is questionable according to the existing single and uniform indicators. New, more relevant "tailored" target values should be suggested for the Eastern part of the Gulf of Finland in order to take into account its natural differences from the Western part of the Gulf.