Biogeochemical functioning of the Baltic Sea

Abstract. Location, specific topography, and hydrographic setting together with climate change strong anthropogenic pressure are the main factors shaping biogeochemical functioning thus also ecological status of Baltic Sea. The recent decades have brought significant changes in First, rising nutrient loads from land second half 20th century led to eutrophication spreading hypoxic anoxic areas, for which permanent stratification water column limited ventilation deep-water layers made favourable conditions. Since 1980s Sea been continuously decreasing. This, however, has so far not resulted improvements oxygen availability deep regions, revealed a slow response time system reduction land-derived loads. Responsible that is low burial efficiency phosphorus at conditions its remobilization sediments when oxic anoxic. This results stoichiometric excess available organic-matter production, promotes growth N2-fixing cyanobacteria turn supports eutrophication. assessment reviews published knowledge on In content, paper covers aspects related carbon, nitrogen, (C, N, P) external loads, their transformations coastal zone, production (eutrophication) remineralization (oxygen availability), role turnover C, P. addition that, this focuses marine CO2 system, structure microbial community, contaminants processes. comprehensive allowed identifying gaps future research needs field biogeochemistry