Abstract
For many coastal areas including the Baltic Sea, ambitious nutrient abatement goals have been set to curb eutrophication, but benefits of such measures were normally not studied in light of anticipated climate change. To project the likely responses of nutrient abatement on eelgrass (Zostera marina), we coupled a species distribution model with a biogeochemical model, obtaining future water turbidity, and a wave model for predicting the future hydrodynamics in the coastal area. Using this, eelgrass distribution was modeled for different combinations of nutrient scenarios and future wind fields. We are the first to demonstrate that while under a business as usual scenario overall eelgrass area will not recover, nutrient reductions that fulfill the Helsinki Commission’s Baltic Sea Action Plan (BSAP) are likely to lead to a substantial areal expansion of eelgrass coverage, primarily at the current distribution’s lower depth limits, thereby overcompensating losses in shallow areas caused by a stormier climate.
Highlights
Marine coastal ecosystems are suffering from ongoing global change, including ocean warming, acidification, deoxygenation, and eutrophication (Rabalais et al 2009), in addition to enhanced storminess and wave energy impinging on shorelines (Young and Ribal 2019)
The Baltic Sea Action Plan (BSAP) committed each member state to nutrient input ceilings to restore the Baltic marine environment by 2021 (Backer et al 2010). It is less well established, whether the proposed reduction goals will be sufficient to result in significant recoveries of valuable ecosystems that have declined in the past, such as eutrophication sensitive seagrass beds that are one prime target for coastal conservation effort
Our scenario modeling indicates that nutrient abatement according to the Baltic Sea Action Plan (BSAP scenario) enhances the occurrence of Z. marina along the Baltic coast of northern Germany
Summary
Marine coastal ecosystems are suffering from ongoing global change, including ocean warming, acidification, deoxygenation, and eutrophication (Rabalais et al 2009), in addition to enhanced storminess and wave energy impinging on shorelines (Young and Ribal 2019). At the European level, several legislative frameworks such as the Water Framework Directive (EC 2000) and the Marine Strategy Framework Directive (EC 2008) have been adopted aiming to achieve a ‘good environmental status’ (GES) in coastal and open ocean waters These directives demand coordinated measures to promote ecosystem recovery and indicate the need for assessing the benefits of environmental rectification. The BSAP committed each member state to nutrient input ceilings to restore the Baltic marine environment by 2021 (Backer et al 2010) It is less well established, whether the proposed reduction goals will be sufficient to result in significant recoveries of valuable ecosystems that have declined in the past, such as eutrophication sensitive seagrass beds that are one prime target for coastal conservation effort.
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