Remediation of a Eutrophic Bay in the Baltic Sea.

Eutrophication of coastal ecosystems is a global problem that often results in bottom water oxygen deficiency and in turn promotes sediment phosphorus (P) release (A). In order to increase sediment P retention, we injected dissolved aluminum into the anoxic sediment of a eutrophic semienclosed bay in the Baltic Sea, thereby inhibiting P recycling and further eutrophication (B). The P concentration in the bay remained at half, as did phytoplankton biomass (C), compared to pretreatment conditions and compared to the reference bay.

Reduction of Baltic Sea nutrient inputs and allocation of abatement costs within the Baltic Sea catchment.

The Baltic Sea Action Plan (BSAP) requires tools to simulate effects and costs of various nutrient abatement strategies. Hierarchically connected databases and models of the entire catchment have been created to allow decision makers to view scenarios via the decision support system NEST. Increased intensity in agriculture in transient countries would result in increased nutrient loads to the Baltic Sea, particularly from Poland, the Baltic States, and Russia.

Scenario analysis on protein consumption and climate change effects on riverine N export to the Baltic Sea.

This paper evaluates possible future nitrogen loadings from 105 catchments surrounding the Baltic Sea. Multiple regressions are used to model total nitrogen (TN) flux as a function of specific runoff (Q), atmospheric nitrogen deposition, and primary emissions (PE) from humans and livestock. On average cattle contributed with 63%, humans with 20%, and pigs with 17% of the total nitrogen PE to land.

Hypoxia-related processes in the Baltic Sea.

Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP.

Searching efficient protection strategies for the eutrophied Gulf of Finland: the combined use of 1D and 3D modeling in assessing long-term state scenarios with high spatial resolution.

An experiment combining the use of two ecosystem models was conducted to search for effective protection strategies for the Gulf of Finland (Baltic Sea). Reference and scenario simulations were first run with a one-dimensional (1D) model for seven main basins of the entire Baltic Sea until steady state was achieved. The obtained basinwise distributions of inorganic nitrogen (N) and phosphorus (P), as well as sediment labile P, were then used to initiate 5-y simulations with a three-dimensional (3D) ecosystem model.

Management options and effects on a marine ecosystem: assessing the future of the Baltic.

We are using the coupled models in a decision support system, Nest, to evaluate the response of the marine ecosystem to changes in external loads through various management options. The models address all the seven major marine basins and the entire drainage basin of the Baltic Sea. A series of future scenarios have been developed, in close collaboration with the Helsinki Commission, to see the possible effects of improved wastewater treatment and manure handling, phosphorus-free detergents, and less intensive land use and live stocks.

Internal ecosystem feedbacks enhance nitrogen-fixing cyanobacteria blooms and complicate management in the Baltic Sea.

Eutrophication of the Baltic Sea has potentially increased the frequency and magnitude of cyanobacteria blooms. Eutrophication leads to increased sedimentation of organic material, increasing the extent of anoxic bottoms and subsequently increasing the internal phosphorus loading. In addition, the hypoxic water volume displays a negative relationship with the total dissolved inorganic nitrogen pool, suggesting greater overall nitrogen removal with increased hypoxia.

Modeling the Baltic Sea eutrophication in a decision support system.

SANBALTS (Simple As Necessary Baltic Long-Term Large-Scale) is a model of the coupled nitrogen and phosphorus cycles. This model has been developed as an integral part of the decision support system Marine Research on Eutrophication's Nest with the overall aim to evaluate management options for reducing Baltic Sea eutrophication. Simulated nutrient and oxygen concentrations as well as transport flows and major biogeochemical fluxes can be analyzed in many different ways, including construction of detailed nutrient budgets and tracing the fate of nutrient inputs.

Hypoxia in the Baltic Sea and basin-scale changes in phosphorus biogeochemistry.

Deep-water oxygen concentrations in the Baltic Sea are influenced by eutrophication, but also by saltwater inflows from the North Sea. In the last two decades, only two major inflows have been recorded and the lack of major inflows is believed to have resulted in a long-term stagnation of the deepest bottom water. Analyzing data from 1970 to 2000 at the basin scale, we show that the estimated volume of water with oxygen, <2 mL L(-1), was actually at a minimum at the end of the longest so-called stagnation period on record.