Biological production and eutrophication of Baltic Sea estuarine ecosystems: The Curonian and Vistula Lagoons

The long-term data on the temporal and spatial changes of chlorophyll and nutrients concentrations, phytoplankton biomass, primary production and mineralization of organic matter in the Curonian and Vistula Lagoons were analyzed using seasonal data to 1994 and monthly data to 2007 at 9–12 stations. A comparison with hydrological (water temperature, salinity, water exchange) and chemical parameters indicate the main abiotic factors which influence the level of biological production and the trophic state of lagoons. Most of the Curonian Lagoon showed the strong summer warming-up of water (higher 20 °C) combined with freshwater conditions, slow-flow velocity and high concentrations of phosphorus which creates conditions for hyperblooms of Cyanobacteria. The biological production of the Vistula Lagoon is below the potentially possible level as the hydrodynamic activity (high-flow velocity) and brackish water prevent the intensive development of Cyanobacteria. The Curonian Lagoon may be considered as hypertrophic water body whereas the Vistula Lagoon is a eutrophic water body.