Meeting Abstract
Climate-induced changes including increasing surface seawater temperatures and decreasing pH are occurring rapidly around the world. It has been suggested that in these near-future ocean conditions, marine organisms will become more vulnerable to infectious diseases. However, no studies have examined the effects of both warming and acidification on the immune response of sea urchins, an ecologically important taxon across many marine ecosystems. This study investigated the effects of warming and acidification on the sea urchin Heliocidaris erythrogramma, a species commonly found in eastern Australia, a region that is experiencing rapid climate-induced change. Sea urchins were exposed to treatments at current and near-future seawater temperature (17 and 23°C) and pH (8.2 and 7.6). After three experimental exposures (1, 15, and 30 days), coelomocyte (cells associated with innate immunity) number and phagocytic capacity (a measure of immune response) were measured (n=5 per treatment). The number of coelomocytes present in coelomic fluid was not significantly different among treatments or exposure. However, at all three exposures the phagocytic capacity of coelomocytes from sea urchins exposed to seawater at ambient temperature and reduced pH was one-third lower than that of sea urchins held at control conditions. Additional data are presently being analyzed to determine the bactericidal activity of these coelomocytes against a common marine pathogen Vibrio anguillarum. Collectively, these parameters provide an evaluation of the ability of H. erythrogramma to respond to immune challenges in a rapidly warming and acidifying marine environment. Supported by the NSF, Australian Academy of Sciences, and the NSW Environmental Trust.
