Effects of CO2-driven sea water acidification on the ecophysiology of neritic calcifiers, using the amphipod Gammarus locusta as a model.

This project will test the hypothesis that sea water acidification, a consequence of increases in the concentration of atmospheric carbon dioxide (CO2), will create sub-lethal physiological stress in marine organisms. The effects of a potential increase in the acidity of coastal waters on the biology of a widespread crustacean, the amphipod Gammarus locusta, will be investigated as an experimental model system. It is almost universally accepted that the continued burning of fossil fuels by industrialized nations around the globe is causing an increase in accumulation of waste carbon dioxide (CO2) within the earth's atmosphere. One direct and well-known consequence of this accumulation is an increase in the average global temperature, caused as the earth's radiated heat energy is trapped within the atmosphere by the excess CO2. Within the marine environment another consequence of this increase in atmospheric CO2 is that more carbon dioxide will dissolve into the surface waters of the ocean. This increase in the amount of carbon dioxide dissolved in the ocean will have a direct impact on the acidity of the sea water. As the oceans become more acidic the chemistry of the water will change and the availability of important ions such as carbonate will be reduced. Dissolved carbonate minerals, particularly calcium carbonate, are extremely important to a wide range of marine organisms which have hard outer shells, such as mussels, oysters, crabs and lobsters. The small crustacean amphipod Gammarus locusta is one such species. This organism makes use of calcium carbonate to generate a new outer skeleton, or exoskeleton, at each moult and consequently this species might be expected to be effected by CO2-driven changes in sea water carbonate chemistry. Any reduction in the rate at which calcium carbonate can be deposited in a new skeleton, especially during crucial juvenile developmental stages, will reduce population growth and species fitness within an ecosystem. This project will consider the potential differential tolerance to CO2-driven sea water acidification of all life stages of this species, from juveniles through to adult. Conventional measurements of whole organism biology, such as individual growth rate, will be combined with the latest molecular techniques to investigate sub-lethal impacts on the ecophysiology of this species. This project will also provide an opportunity to test and modify the necessary culture techniques to investigate the effects of sea water acidification on other stages in the life cycle of crustaceans, including reproduction and fertilization. It will also permit 'high-CO2' experiments to be conducted on other important benthic calcifying species with longer life spans, for example the mussel Mytilus edulis. This project will be conducted at the National Oceanography Centre Southampton (NOCS), one of the centres of excellence for marine science in the UK and with an established track record of research into CO2-driven changes in seawater chemistry and the ecophysiology of marine organisms.