Ocean acidification (OA) is a serious threat to marine biodiversity. Most of the OA research, however, investigates impacts of predicted future pH... » More

Ocean acidification (OA) is a serious threat to marine biodiversity. Most of the OA research, however, investigates impacts of predicted future pH values on survival and performance of marine species, while less attention is paid to the possible effects that OA has in its current extent. Shells of different organisms are widely used as environmental proxies, describing e.g. past salinity and temperature conditions. Macoma balthica is a key species in the low-diversity Baltic Sea and our aim is to investigate the potential of Macoma shells as indicators of past climate and pH in the Baltic, to test if the effects of OA can already be seen through changes in the ion composition of Macoma shells. Changes in the calcification capacity of Macoma are explored by determination of trace element ratios in benthic monitoring samples from the 1960s onwards. Shells of a certain size class and from a defined depth range are analysed from the Gulf of Finland since the beginning of the monitoring. To compare location-specific patterns, the corresponding analyses are conducted on shells from different areas in the Baltic along a salinity gradient. This helps us to develop an understanding of the current state of acidification in the Baltic.

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