Effects of storm-induced sand scour on Patella vulgata off south-west Britain

Abstract

This study investigates the impacts of storm-induced sand-scour on common limpets (Patella vulgata) off south-west Britain, focussing particularly on the physical impacts of this process, as well as shore recovery. Unusually polished limpets were found living on a rocky shore (Westcombe Beach, South Devon) following a series of large storms that occurred from December 2013 to mid-February 2014. The extent of the storms was completely unprecedented, and it was one of the most exceptional periods of winter rainfall in Englandin at least 248 years when records began. It was clear that the limpets and surrounding epilithic communities at Westcombe Beach had been abraded by suspended particles in the storm waves. Limpets on an exposed shore and a sheltered shore were investigated by means of shell measurements and compression tests to determine differences in thickness and strength in months following the storms. Photoquadrats were taken on the storm-exposed shore to monitor living limpet clusters and associated communities. Sand-scoured shells were significantly thinner for their size than non-scoured shells, but these increased in thickness as time passed after the storms. Sand-scour did not influence shell strength between the two sites, though sand-scoured shells characteristically flaked and crumbled under compressive force. It was surprising to find that sand-scoured limpets were able to repair their periostracum on the uppermost parts of their shell, although the mechanisms for doing this are not known. Given that global climate change is expected to increase coastal storms, these findings shed light on the likely impacts of increased sand-scour on exposed shores.