Climate change alters shellfish reef communities: A temperate mesocosm experiment

Highlights: • Climate change will cause significant changes to rocky shore diversity. • Outdoor mesocosms were used to test predictions of warming and ocean acidification. • Elevated carbon dioxide in the atmosphere reduced the growth of the native mussels. • Warming and carbon dioxide influenced the species that colonised the mussels. Climate change is expected to cause significant changes to rocky shore diversity. This study used outdoor mesocosms to test the predictions that warming and ocean acidification will alter the responses of native Trichomya hirsuta and introduced Mytilus galloprovincialis mussels, and their associated communities of infauna. Experiments consisted of orthogonal combinations of temperature (ambient 22 °C or elevated 25 °C), pCO₂ (ambient 400 μatm or elevated 1000 μatm), mussel species (T. hirsuta or M. galloprovincialis), and mussel configuration (native, introduced, or both), with n = 3 replicates. Elevated pCO₂ reduced the growth of T. hirsuta but not that of M. galloprovincialis, and warming and pCO₂ influenced the infauna that colonised both species of mussels. There was a reduction in infaunal molluscs and an increase in polychaetes; there was, however, no effect on crustaceans. Results from this study suggest that climate-driven changes from one mussel species to another can significantly influence infaunal communities.