Baltic Sea affected by multiple stressors
During the past decades many of the world´s marine ecosystems have experienced large-scale reorganizations caused by intensive exploitation of marine resources in combination with climate changes.
One of the most effected ecosystems is the Baltic Sea, which has been affected by a combination of e.g. persistent eutrophication and intensive fishing, and during the last two decades of the 20th century being exposed to one of the world’s fastest rates of warming.
Model projections show that this region will be subject to accelerated climate changes, including atmospheric warming and changes in precipitation during the 21st century.
The question is how marine ecosystem processes and the provisioning of ecosystem services will be affected by these changes.
Multimodel approach links regional drivers
The team 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, previously developed within ECOSUPPORT, were, in combination with three nutrient load scenarios, used to drive an ensemble of three state-of-the-art regional biogeochemical models (BGMs) (including BNI-developed BALTSEM). An Ecopath with Ecosim food web model (BNI-developed BaltProWeb) was then forced with the BGM results from different nutrient-climate scenarios in combination with two different cod fishing scenarios.
Ecological surprises and the importance of management
The study showed that regional drivers could have a large impact on defining the future of the Baltic Sea, but that climate induced-changes in hydrodynamic conditions still set boundaries for food web structure and function.
Regional management was shown to play an important role in determining the future of the ecosystem as different scenarios for management of fishing pressure and nutrient loads (e.g. BAU – Business As Usual – and BSAP – implementation of the HELCOM Baltic Sea Action Plan) led to different responses in the food web.
A combination of intensive cod fishing and high nutrient loads where projected to, by the end of the 21st century, lead to a strongly eutrophicated and sprat-dominated ecosystem. On the other hand, a combination of low cod fishing and low nutrient loads resulted in a cod-dominated ecosystem with eutrophication levels close to present.
As regional and global drivers have the potential to lead to large scale impacts and possible thresholds, causing sudden ecosystem surprises, the results acknowledges the importance of management and the need to address the risk for ecological surprises, including the risk of non-indigenous species invasions that may lead to large changes in the ecosystem.
Download the article "Combined effects of global climate change and regional ecosystem drivers on an exploited marine food web" here
Link to a list of additional BNI-publications from the ECOSUPPORT project
Below are some reports from the BNI Technical Series describing BALTSEM:
Link to a list of BNI publications related to the BaltProWeb