Ocean acidification (OA) in the Baltic Sea from a Swedish perspective

This report is produced as part of the project “Baltic Sea Acidification Mitigation” (BALSAM), supported by the Swedish Institute. The aim of this report and other, corresponding reports (produced for the other countries participating in BALSAM) is primarily to inform environmental NGOs and other stakeholders interested in environmental issues. The aim of this country report is to provide information on Ocean Acidification (OA) in the Baltic Sea with special emphasis on Swedish waters, and to provide an insight into the research and monitoring that are the basis of the current understanding of OA in these waters. This is done as support for campaigning towards mitigation of greenhouse gases and protection of the seas. Whereas this document is not a comprehensive literature review, it is intended as a timely guide to the concept of OA, and does contain key publications and links to further indepth reading and sources of additional information.

Ocean acidification (OA) comes in the wake of climate change as the result of increased atmospheric CO2, which is taken up by the oceans. About 30 % of the CO2 that is emitted to the atmosphere because of human activity ends up in the waterbodies. Part of the CO2 reacts with water, and forms carbonic acid. Some of the carbonic acid dissociates, resulting in bicarbonate and in hydrogen ions. This process leads to acidification (lower pH, i.e. higher concentration of hydrogen ions). Organisms in the oceans are adapted to the pH-conditions that have prevailed in the seas prior to this human driven acidification-process. Especially calcifying organisms are sensitive to acidification, but the physiology of many other organisms can be affected as well, as can the complex ecological interactions between organisms. In a global setting, ongoing and projected effects of OA have been extensively described in several IPCC reports (e.g. IPCC, 2018, 2019).

In Sweden, an interdisciplinary review on causes and consequences of OA in the Swedish Seas (including both the Baltic Sea and the more saline waters of Skagerrak at the Swedish west coast), as well as knowledge gaps, was published relatively recently as part of work supported by the Royal Swedish Academy of Sciences (Havenhand et al. 2017). Additionally, in the same context, a scientific review focusing on the ecological consequences of OA was published by Havenhand et al. in 2019. A policy brief1 on OA in the Baltic Sea was furthermore published in 2020 by The Baltic Sea Centre of Stockholm University (Gustafsson & Winder 2020). This policy brief provides a general view of OA as support for policy making.

Reinikainen M., 2021. Ocean acidification (OA) in the Baltic Sea from a Swedish perspective. Airclim, Swedish Institute. Report.

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