Risks to marine biotas and ecosystems in European seas are projected to impact important ecosystem services . Elevated CO2 levels predicted at 4ºC GWL will affect the C/N ratio of organic-matter export and, hence, the efficiency of the biological pump , depending on the shifts in plankton composition and, hence, food-web structure . Atlantic herring  will benefit with enhanced larval growth and survival from indirect food- web effects , whereas Atlantic cod  will face overall negative impacts  . Anoxic dead zones in the Black  and the Baltic  seas are projected to increase, for example, by 5% in the Baltic Sea at 4°C GWL . Europe's coastal vegetated 'blue carbon' ecosystems  are highly vulnerable , particularly in microtidal areas such as the Baltic and Mediterranean coast. Losses are projected for Posidonia oceanica seagrass habitats in the Mediterranean by up to 75% at 2.5°C GWL  . The Wadden Sea, the world's largest system of intertidal flats, is projected to reduce in surface area and height, as the sediment transport capacity limits the possibility of growth with rapidly rising sea levels . For the Dutch Wadden Sea, the critical rate of 6-10 mm yr-1, at which intertidal flats will start to 'drown', will be reached by 2030 at 1.5°C GWL , or even earlier through subsidence due to human activities . European coastal zones provided a total of 494 billion EUR of ecosystem services in 2018, and 4.2-5.1% of this value will be lost due to coastal erosion by 2100 at 2.5°C and 4.6°C GWL, respectively  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report