The Baltic Sea is today one of earth’s most endangered semi enclosed seas as a result of increased anthropogenic pressure manifested in e.g. eutrophication, overfishing, biodiversity loss, toxic pollutants and alien species. Eutrophication causes hypoxia (oxygen concentration less than 2 mg L-1) in bottom waters, killing benthic organisms and altering biogeochemical cycles. It is considered one of the most severe threats to marine ecosystems. The role of humans and climate in driving the eutrophication and hypoxia in the Baltic Sea needs to be understood, especially at present when global warming in the basin is projected to be around 3-5°C during the course of the 21st century (HELCOM 2007). The Baltic Sea coastal zone contains at present >20% of all identified hypoxic sites worldwide and shows an increasing trend since 1950, but data on long-term trends of hypoxia are lacking. Knowledge of pristine nutrient conditions in the Baltic coastal zone is essential to set appropriate targets within the EU Water Framework Directive and limitations on nutrient emissions for countries bordering the Baltic Sea within the Baltic Sea Action Plan.
This proposed project will disentangle the role of human- and climate-driven processes that result in events of eutrophication and hypoxia in the Baltic Sea during the last 2000 years. Research emphasis is on the coastal zone, where responses to human activities on land can be expected to be first recorded, and its coupling with the open Baltic Sea, and will be accomplished by focusing on four over-arching objectives:
• The long-term trends in coastal hypoxia in time and space
• The driving forces for hypoxia in the coastal zone through time
• Influence of changes in land-use on coastal waters and interactions between the coast and open Baltic Sea
• Background nutrient conditions in the coastal zone as a target for sustainable Baltic Sea management
There is a strong need for interdisciplinary work to solve the environmental problems of the Baltic Sea and our results will be of interest to a wide range of scientists working with sustainability within the Baltic Sea drainage area as well as management authorities.