Integrated modelling of ocean acidification and warming impacts on fish species and the marine food web in the Barents Sea

Chair: Heidi Pethybridge

Stefan Koenigstein (1,3)*, Hauke Reuter (2), Hans-Otto Pörtner (3), Stefan Gößling-Reisemann (
1)

1 Department of Resilient Energy Systems / Sustainability Research Centre (artec), University of Bremen, Bremen, Germany
2 Department of Ecological Theory and Modelling, Leibniz Center for Tropical Marine Ecology (ZMT), Bremen, Germany
3 Integrative Ecophysiology section, Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

Background
Research on the combined effects of multiple environmental and anthropogenic stressors in marine ecosystems is of high importance for assessing the future development of the oceans and their ecosystem services. In the Barents Sea, economically important fish stocks are subject to temperature-dependent fluctuations, and community shifts related to ocean warming are already observed. Continued warming and strong ocean acidification are projected for the next decades and are anticipated to trigger further changes in the community structure of marine ecosystems and their dynamics with corresponding impacts on human societies.

Methods
We developed a multi-species model, which integrates temperature and pH effects on biological processes such as growth, reproduction and recruitment, integrating impacts observed in different life stages of Atlantic cod, herring and zooplankton species and linking species responses via the food web. Changes in ecosystem structure and dynamics and the consequences of climate change and harvesting scenarios for ecosystem resilience and the provision of ecosystem services are explored.

Findings
The model reproduces current biomass estimations and typical interdependent oscillations of fish stocks in the Barents Sea. Warming promotes temperate fish species, but has negative effects on polar species. Ocean acidification is projected to have negative impacts on some fish stocks through additional metabolic losses, leading to some fish stocks winning, some losing. Changes in food web dynamics indirectly impact some marine mammal and seabird species, and cause decreases in secondary production by zooplankton and carbon export from the food web.

Conclusions

Ocean acidification and warming can trigger changes in higher trophic level dynamics and affect ecosystem functioning. The integrative model helps to interpret ocean acidification impacts in the context of interactions with decadal climate variations, warming and resource extraction by fisheries, illustrating how multiple drivers affect ecosystems and the provisioning of ecosystem services to human societies under global change scenarios.