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| Changes in climate, in combination with intensive exploitation of marine resources, have caused large-scale reorganizations
in many of the world’s marine ecosystems during the past decades. The Baltic Sea in Northern Europe is one
of the systems most affected. In addition to being exposed to persistent eutrophication, intensive fishing, and one of
the world’s fastest rates of warming in the last two decades of the 20th century, accelerated climate change including
atmospheric warming and changes in precipitation is projected for this region during the 21st century. Here, we used
a new multimodel approach to project how the interaction of climate, nutrient loads, and cod fishing may affect the
future of the open Central Baltic Sea food web. Regionally downscaled global climate scenarios were, in combination
with three nutrient load scenarios, used to drive an ensemble of three regional biogeochemical models (BGMs). An
Ecopath with Ecosim food web model was then forced with the BGM results from different nutrient-climate scenarios
in combination with two different cod fishing scenarios. The results showed that regional management is likely to
play a major role in determining the future of the Baltic Sea ecosystem. By the end of the 21st century, for example,
the combination of intensive cod fishing and high nutrient loads projected a strongly eutrophicated and spratdominated
ecosystem, whereas low cod fishing in combination with low nutrient loads resulted in a cod-dominated
ecosystem with eutrophication levels close to present. Also, nonlinearities were observed in the sensitivity of different
trophic groups to nutrient loads or fishing depending on the combination of the two. Finally, many climate variables
and species biomasses were projected to levels unseen in the past. Hence, the risk for ecological surprises needs to be
addressed, particularly when the results are discussed in the ecosystem-based management context. | |
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