Baltic Sea groundwater discharge for improving the management of Europe's coasts
Groundwater will flow towards the sea wherever the hydraulic gradient land is above sea level and permeable paths connect continental aquifers to the oceans. This subsurface flow of water allows dissolved material to be transported from the continents into the world's oceans. Although studies have shown that unmonitored waters enter the Baltic Sea via this route, research into the importance of submarine groundwater discharge (SGD) has been limited. To address this lack of research, the EU-funded project SGDBALTIC (The importance of submarine groundwater discharge for the southwestern Baltic Sea) surveyed the south-western Baltic for SGD and measured the associated fluxes of nutrients and selected major and trace elements. Project benefactors focused the effort on Eckernförde Bay because of its high concentration of SGD locations. Various meters were used to measure fluxes in order to determine the total yearly SGD input into the Bay. They obtained various nutrient concentrations, namely silicon, phosphate and nitrogen. The SGDBALTIC team calculated the Bay's annual SGD-based nitrogen and phosphate fluxes, and then compared them with the total water-based nitrogen and phosphorous fluxes in the German Baltic Sea. About 17 % of the Bay's total nitrogen and 22 % of its phosphorous fluxes enter the German Baltic Sea. Findings showed that nitrogen originated from groundwater with high levels of nutrients due to fertiliser used in agriculture. Researchers propose a reduction in the use of fertilisers or a removal of groundwater nutrients to reduce SGD-based nutrient fluxes in the south-western Baltic Sea. SGDBALTIC contributed to knowledge of the link between the continents and oceans. This will have important implications for managing the coastal regions of Europe in light of the EU policy objectives.
Keywords
Baltic Sea, submarine groundwater discharge change, SGDBALTIC, nutrient fluxes
