Sea urchins in a high-CO2 world: the influence of acclimation on the immune response to ocean warming and acidification.

Climate-induced ocean warming and acidification may render marine organisms more vulnerable to infectious diseases. We investigated the effects of warming and acidification on the immune response of the sea urchin Heliocidaris erythrogramma Sea urchins were gradually introduced to four combinations of temperature and pHNIST (17°C/pH 8.15, 17°C/pH 7.6, 23°C/pH 8.15 and 23°C/pH 7.6) and then held in temperature-pH treatments for 1, 15 or 30 days to determine if the immune response would adjust to stressors over time. Coelomocyte concentration and type, phagocytic capacity and bactericidal activity were measured on day 1, 15 and 30 with different sea urchins used each time. At each time point, the coelomic fluid of individuals exposed to increased temperature and acidification had the lowest coelomocyte concentrations, exhibited lower phagocytic capacities and was least effective at inhibiting bacterial growth of the pathogen Vibrio anguillarum Over time, increased temperature alleviated the negative effects of acidification on phagocytic activity. Our results demonstrate the importance of incorporating acclimation time to multiple stressors when assessing potential responses to future ocean conditions and indicate that the immune response of H. erythrogramma may be compromised under near-future ocean warming and acidification.

In situ observations of a possible skate nursery off the western Antarctic Peninsula.

A dense aggregation of skate egg cases was imaged during a photographic survey of the sea floor along the western Antarctic Peninsula in November 2013. Egg cases were noted in a narrow band between 394 and 443 m depth. Although some skate species in other oceans are known to utilize restricted areas to deposit eggs in great numbers, such nurseries have not been described in the Southern Ocean.