Nutrient Levels and Eutrophication of the Romanian Black Sea Waters (2006-2011) - Assessment Related to the Marine Strategy Framework Directive Implementation

Abstract

The assessment of the current nutrient levels and eutrophication of the Romanian Black Sea waters, as part of the Marine Strategy Framework Directive implementation, was based on data acquired during 2006-2011 from the monitoring network stations consisting of 36 stations along the Romanian littoral. Additionally, were collected daily (for chemistry) and bi-weekly (for phytoplankton) data from the Constan’a station. The trends were analyzed based on historical data (1964/1980-2011) from the East Constanța transect. The inorganic phosphorus content is influenced by the Danube’s and WWTPs’ input. Due to different flows, the fluvial input is more significant. On the long-term, decreased concentrations compared to the values of the 1960s, reference period for the good quality of the Romanian Black Sea waters, were observed. These low values give to phosphorus the feature of a limitative element for the phytoplankton’s proliferation. The inorganic nitrogen content is mainly influenced by the Danube’s input. Seasonally and on a restricted area, we found in the neighborhood of WWTPs higher ammonia concentrations. On the long-term, we observed the decreasing concentrations up to the level of 1991-1992, when the intensity of the eutrophication started to drop. Therefore, the intensity and number of the monospecific blooms have decreased, the mixed blooms phenomena and the increasing diatoms proportion in the phytoplanktonic populations occurred and, consequently, the eutrophication has been slightly reduced. Dinoflagellates’ proportion was reduced, but still, in the summer, they can reach 40% from the total phytoplankton. Thus, the ecosystem recovery is still fragile and could be easily destabilized by the influence of the anthropogenic pressures and climate changes.