Suchergebnisse

A longstanding recognition of eutrophication as the most common threat to the entire Baltic Sea has led to the international agreement on nutrient load reductions within the Baltic Sea Action Plan. The nutrient load reductions were based on quantitative estimates of the "maximum allowed nutrient inputs" evaluated with a help of the decision support system (DSS) Baltic Nest developed within the MARE (Marine Research on Eutrophication) program. As demonstrated by a comparison to available data derived from observations, the marine biogeochemical model SANBALTS (Simple As Necessary Baltic Long-Term large-Scale) used in this evaluationis capable to realistically simulate both contemporary and pre-industrial trophic states of the Baltic Sea. A key to successful performance of SANBALTS lays in accounting for major sources and sinks that determine the size of internal nutrient pools and, thus, govern the large scale Baltic Sea eutrophication. Particularly, the most important phenomena that have to be reproduced by eutrophication models are a) spatial gradients of environmental conditions and limiting nutrients, b) interconnectivity of the major Baltic Sea basins, c) sporadic ventilation of the hypoxia prone deep-water layers with saltwater inflows, d) redox alterations of the coupled nitrogen and phosphorusbiogeochemical cycles, and d) nitrogen fixationby cyanobacteria.At the same time, both a ratherhigh aggregation of ecosystem variables (organic and inorganic forms of nutrients without explicit description of biota) and their correspondent spatial-temporal averaging (annual within homogeneous basins) implemented in SANBALTS make this model not appropriate enough for further revision and elaboration of the BSAP. Because such revision has also to take into consideration indicators required by the Marine Strategy Framework Directive (MSFD) of the European Union and characterized by higher spatial and temporal resolution, e.g.basin-wise winter surface nutrient concentrations and summer phytoplankton biomasses, and because of a necessity to factor in the possible effects of climate fluctuations, the appropriate model must simulate changes in ecosystem seasonal dynamics occurring over tens of years in response to both nutrient load reductions and climate changes. In principle, the continuing development of computing resources has made it feasible to implement for such purposes three-dimensional coupled physical-biogeochemical models with a relatively high resolution. However, with such models a simulation of the entire Baltic Sea over several decades still requires many days of computation even at super computer centers, which greatly hinders numerical experimentation needed for both model calibration and sensitivity analysis, including scenario responses. Therefore, there is a need for the model that is both reliable and convenient enough to be used for the revision of BSAP and implementation of MSFD,as well as for similar managerial tasks within an ecosystem approach. To serve this need, the model should be computationally fast for allowing multiple numerical runs necessary for finding and testing suitable distributions of the water-protection measures. Furthermore, for a building of credibility necessary in the national deliberations and international negotiations it should also be publicly accessible through the decision support system Nest allowing to any interested party running hindcast and scenario experiments as well as visualize its results. For these purposes, we present here the latest developments of the BAltic sea Long-Term large Scale Eutrophication Model (BALTSEM), which captures the main features of the Baltic Sea eutrophication, and now servesas a next generation marine model in the Baltic Nest system. These results as well as hindcast for 1850-2006 and future scenarios can be reproduced and analyzed on-line. Since BALTSEM performance at long-term scales has already been presented by Eilola et al. (2011a) and Gustafsson et al. (2012), this paper is especially focused on a seasonal scale.

The occurrence of regime shifts in marine ecosystems has important implications for environmental legislation that requires setting reference levels and targets of quantitative restoration outcomes. The Baltic Sea ecosystem has undergone large changes in the 20 th century related to anthropogenic pressures and climate variability, which have caused ecosystem reorganization. Here, we compiled historical information and identified relationships in our dataset using multivariate statistics and modeling across 31 biotic and abiotic variables from 1925 to 2005 in the Central Baltic Sea. We identified a series of ecosystem regime shifts in the 1930s, 1970s, and at the end of the 1980s/beginning of the 1990s. In the long term, the Central Baltic Sea showed a regime shift from a benthic to pelagic-dominated state. Historically, benthic components played a significant role in trophic transfer, while in the more recent productive system pelagic–benthic coupling was weak and pelagic components dominated. Our analysis shows that for the entire time period, productivity, climate, and hydrography mainly affected the functioning of the food web, whereas fishing became important more recently. Eutrophication had far-reaching direct and indirect impacts from a long-term perspective and changed not only the trophic state of the system but also affected higher trophic levels. Our study also suggests a switch in regulatory drivers from salinity to oxygen. The "reference ecosystem" identified in our analysis may guide the establishment of an ecosystem state baseline and threshold values for ecosystem state indicators of the Central Baltic Sea.

Effectively reducing cumulative impacts on marine ecosystems requires co-evolution between science, policy and practice. Here, long-term social–ecological changes in the Baltic Sea are described, illustrating how the process of making the ecosystem approach operational in a large marine ecosystem can be stimulated. The existing multi-level governance institutions are specifically set up for dealing with individual sectors, but do not adequately support an operational application of the ecosystem approach. The review of ecosystem services in relation to regime shifts and resilience of the Baltic Sea sub-basins, and their driving forces, points to a number of challenges. There is however a movement towards a new governance regime. Bottom-up pilot initiatives can lead to a diffusion of innovation within the existing governance framework. Top-down, enabling EU legislation, can help stimulating innovations and re-organizing governance structures at drainage basin level to the Baltic Sea catchment as a whole. Experimentation and innovation at local to the regional levels is critical for a transition to ecosystem-based management. Establishing science-based learning platforms at sub-basin scales could facilitate this process.

Eutrophication is one of the most important anthropogenic pressures impacting coastal seas. In Europe, several legislations and management measures have been implemented to halt nutrient overloading in marine ecosystems. This study evaluates the impact of freshwater nutrient control measures on higher trophic levels (HTL) in European marine ecosystems following descriptors and criteria as defined by the Marine Strategy Framework Directive (MSFD). We used a novel pan-European marine modeling ensemble of fourteen HTL models, covering almost all the EU seas, under two nutrient management scenarios. Results from our projections suggest that the proposed nutrient reduction measures may not have a significant impact on the structure and function of European marine ecosystems. Among the assessed criteria, the spawning stock biomass of commercially important fish stocks and the biomass of small pelagic fishes would be the most impacted, albeit with values lower than 2.5%. For the other criteria/indicators, such as species diversity and trophic level indicators, the impact was lower. The Black Sea and the North-East Atlantic were the most negatively impacted regions, while the Baltic Sea was the only region showing signs of improvement. Coastal and shelf areas were more sensitive to environmental changes than large regional and sub-regional ecosystems that also include open seas. This is the first pan-European multi-model comparison study used to assess the impacts of land-based measures on marine and coastal European ecosystems through a set of selected ecological indicators. Since anthropogenic pressures are expanding apace in the marine environment and policy makers need to use rapid and effective policy measures for fast-changing environments, this modeling framework is an essential asset in supporting and guiding EU policy needs and decisions.