NEWS
During two days Ecochange scientists have presented and discussed results from the extensive ongoing research. Creating a picture of the effects of climate changes on the food web of the Baltic Sea is like building a large jigsaw puzzle. Every little piece contributes to the overall picture. But the Baltic ecosystem is complex, and the more knowledge is shared, the more it grows as a never-ending story.
The climate is changing, and the research programme Ecochange focuses on its ecological effects in the Baltic Sea. Today the Baltic is struggling with several severe environmental problems, with emphasis on eutrophication in the south and environmental pollutants in the north. Ecochange explores the impact of a changing climate on an already disturbed ecosystem.
Increasing temperature, higher precipitation, changing wind conditions and less ice cover are all direct effects of the climate changes. These effects can in turn bring on changes in light climate, salinity, dissolved organic carbon (DOC) and pH. Obviously, the changes in climate will have a large impact on the Baltic Sea ecosystem. The question is how these changes will appear, and what the consequences will be.
Brown, carbon rich water
Marine phytoplankton stand for 50 percent of the global primary production, and the production is highest in coastal areas. In shallow areas the benthic primary production is important, and also sensitive to light conditions. Browner water will definitely be the case in coastal areas in the north, due to increasing inflow of fresh water. This will alter the light conditions, and is expected to affect the importance of primary production. Furthermore, there are heterotrophic bacteria that are sensitive to the light climate. Therefore, it is beyond dispute that changes in light conditions will have an impact on the base of the food web.
Since the increasing inflow of fresh water also carries DOC, this will favor heterotrophic bacteria, while phytoplankton production is expected to be lower due to poor light conditions. The climate changes will therefore, primarily in the north, lead to a shift in the base of the marine food web, from phytoplankton to bacteria living on terrestrial carbon.
Changes and adaptation
There will also be changes higher up in the food web, leading to shifts in species composition on several levels. The relationship between small and large phytoplankton will be altered, which will lead to changes in food quality for zooplankton, and further up for small fish. In the southern parts of the Baltic the cyanobacteria, normally regarded as low quality food for zooplankton, are expected to increase.
An important but often forgotten aspect is the capability of different species to adapt to new environment conditions. The time aspect of this is relatively unknown. An interesting example of this is northern pike, where a part of the coastal population migrates to freshwater to reproduce. These fish have a distinct homing behavior, which means that they return to the same waters where they once were born. The different populations are therefore separated, and differences in size that have evolved have been proven to be signs of genetic differences. The time aspect of this type of process is important to discuss in the climate change context, but is so far relatively unknown.
Organic pollutants in an altered food web
Changes in the species composition will have an impact on how organic pollutants are distributed in the food web. For example, the invading polychaete worm Marenzelleria, now common in all coastal areas of the Baltic Sea, can accumulate more mercury than other benthic fauna. What the ecological effect of this worm’s capacity is in the natural environment is unknown.
Organic pollutants are adsorbed to DOC, and the increasing amount of DOC will probably affect the amounts and quality of the adsorbed pollutants. The quality of DOC differs from the south to the north in the Baltic Sea, and when the amounts of DOC increases the sorption characteristics most likely will change. These findings can be used to develop new tools to monitor the environment.
Field and mesocosm studies
Within Ecochange , studies are performed in the field, in the laboratory and using different types of mesocosms. The Baltic Sea of today shows a gradient, from south to north, in salinity, light conditions and the proportion between primary producers and heterotrophic bacteria. There is a lot to learn about the future of the Baltic by studying all three basins, since the present conditions in the northernmost part, in many ways correspond to predicted conditions further south. Therefore field studies out at sea and in coastal areas along the south-to-north gradient are a very important approach in Ecochange to understand the potential of species to interact and adapt in their natural environment.
To reduce the complexity of the natural environment, laboratory and mesocosm studies were used to explore different climate scenarios. All together, the combination of different methods within Ecochange has step by step increased the knowledge of the effects of the climate induced changes in the complex food web of the Baltic Sea.
Managing the future
Ecochange has grasped over a large and complicated problem. The work resembles building a jigsaw puzzle, where every small piece is needed to reveal the overall picture. The programme is in a phase of dissemination, and during the coming years more pieces will be placed in the puzzle. Perhaps the most important part of the work is yet to be done: to make sure that the environmental management authorities can make use of the comprehensive information produced within Ecochange, in planning the management of the future Baltic Sea.
