The effects of ocean acidification on valve strength in chitons (Polyplacophora)

Abstract

Ocean acidification, the change in ocean chemistry associated with an increase in atmospheric pCO2, is predicted to have harmful impacts on marine life. In this study, I measured the force required to fracture the protective valves of two chiton species (Mopalia muscosa and Mopalia lignosa) after ten days of exposure to control conditions and conditions of raised pCO2. I measured this effect both on valves from freshly sacrificed animals, and on valves that had been dissected prior to treatment. My results show that dissolution of previously dissected valves effects valve strength in M. muscosa, but not in M. lignosa. Both species may compensate for the effects of dissolution in lowered pH treatments by actively depositing more shell material. M. musocsa valves are also, over all treatments, stronger than M. lignosa valves. The variation in baseline strength, and in response to ocean acidification, has implications for the future chiton community in the Northeast Pacific. Additionally, my results call for further research on the physiological tradeoffs of increased shell deposition and the ecological impacts of differential responses to ocean acidification.