EGU2020-19063
https://doi.org/10.5194/egusphere-egu2020-19063
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climate change and recovery from eutrophication reduce benthic fauna and carbon processing in a coastal sea

Eva Ehrnsten1,2, Alf Norkko1,2, Bärbel Müller-Karulis1, Erik Gustafsson1, and Bo Gustafsson1,2
Eva Ehrnsten et al.
  • 1Stockholm University Baltic Sea Centre, Sweden (eva.ehrnsten@su.se)
  • 2Tvärminne Zoological Station, University of Helsinki, Finland

Nutrient loading and climate change affect coastal ecosystems worldwide. Unravelling the combined effects of these pressures on benthic macrofauna is essential for understanding the future functioning of coastal ecosystems, as it is an important component linking the benthic and pelagic realms. In this study, we extended an existing model of benthic macrofauna coupled with the physical-biogeochemical BALTSEM model of the Baltic Sea to study the combined effects of changing nutrient loads and climate on biomass and metabolism of benthic macrofauna historically and in scenarios for the future. Based on a statistical comparison with a large validation dataset of measured biomasses, the model showed good or reasonable performance across the different basins and depth strata in the model area. In scenarios with decreasing nutrient loads according to the Baltic Sea Action Plan, but also with continued recent loads (mean loads 2012-2014), overall macrofaunal biomass and carbon processing were projected to decrease significantly by the end of the century despite improved oxygen conditions at the seafloor. Climate change led to intensified pelagic recycling of primary production and reduced export of particulate organic carbon to the seafloor with negative effects on macrofaunal biomass. In the high nutrient load scenario, representing the highest recorded historical loads, climate change counteracted the effects of increased productivity leading to a hyperbolic response: biomass and carbon processing increased up to mid-21st century but then decreased, giving almost no net change by the end of the 21st century compared to present. The study shows that benthic responses to environmental change are nonlinear and partly decoupled from pelagic responses and indicates that benthic-pelagic coupling might be weaker in a warmer and less eutrophic sea.

How to cite: Ehrnsten, E., Norkko, A., Müller-Karulis, B., Gustafsson, E., and Gustafsson, B.: Climate change and recovery from eutrophication reduce benthic fauna and carbon processing in a coastal sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19063, https://doi.org/10.5194/egusphere-egu2020-19063, 2020

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