Blue mussels from the Kiel Fjord (Baltic Sea), where seawater pH tends to be low, were able to maintain growth rates when exposed to ocean acidification conditions (pH 7.7). in addition, juvenile mussels in the fjord settle mostly in summer when pH is lowest. The findings suggest that mussels may be able to cope with ocean acidification levels projected for the end of this century, if food supply is sufficient. However, further acidification of the Kiel Fjord and other productive estuarine habitats could impair calcification and settlement of young mussels there, and increase the dissolving of their shells. (Laboratory study)