Eutrophication in the Baltic Sea from area-specific biological effects to interdisciplinary consequences

The semi-enclosed topography and the strong anthropogenic pressures make the Baltic Sea vulnerable to environmentally induced ecological changes. The large-scale nutrient overenrichment is one of the most serious threats against the health and future perspectives of the Baltic Sea ecosystem. To combat the eutrophication in a complex marine ecosystem, an interdisciplinary agenda is needed. Co-operation must function between the fields of natural science and socio-economy, and between science and management. For a complete understanding of the eutrophication process and possibilities for remedies, the linkages between ecology and economy is essential. Gaps in communication between science and decision-makers are other obstacles to overcome. The DPSIR-approach (drivers, pressure, state, impact, response) is one way to conceptualize environmental changes and present information in a comprehensive way for society. For a comprehensive analysis of the eutrophication-related processes in the Baltic Sea, the problem is here confronted both in general terms on a basinwide scale and in detail on regional scales. The complexness of eutrophication is illustrated in a general conceptual model, where the pathways from natural science to human society and management options are presented. The model is intended as an interdisciplinary communication base. To pinpoint regional differences, the Baltic Sea is divided into nine sub-regions for area-specific analyses. Based on publicly available papers and reports, the effects and duration of the nutrient over-enrichment are described for each sub-region. The present state of any particular area is summarised in regional conceptual models, which are updated to cover the present situation (2004). For further detection of eutrophication-related trends on a site-specific level, monitoring programmes are important sources of information. Eutrophication is a problem in the entire Baltic Sea area, but the effects and consequences varies between sub-basins. Positive measurements and potential recovery require action both on basinwide and regional scales. To widen the awareness between scientific disciplines and to present the problem to society, principal and site-specific conceptual models are important starting points.