Mussels are popular seafood in northern Germany. Mussels in their blue-black shells, are found in tidal regions of the coastal zones. Like many creatures in the oceans, which protect themselves with a calcareous shell from predators, mussels are endangered by the increasing acidification of seawater caused by the uptake of additional carbon dioxide from the atmosphere which is dissolved in seawater. Mussels are very sensitive to a decline in pH in early life stages. One important reason for this is the enormous calcification rate in the larval stage: between the first and second day of life they form a calcified shell, which corresponds to the weight of the rest of their body. This process is studied by scientists from Kiel and published in the international journal Nature Communications.