Can early exposure to stress enhance resilience to ocean warming in two oyster species?

Abstract

Securing economically and ecologically significant molluscs, as our oceans warm and acidify due to climate change, is a global priority. South eastern Australia receives warm water in a strengthening East Australia Current and so resident species are vulnerable to elevated temperature and marine heat waves. This study tested whether oysters pre exposed to elevated temperature or heat stress enhances resilience to ocean warming later in life. Two Australian species, the flat oyster, Ostrea angasi, and the Sydney rock oyster, Saccostrea glomerata, were given a mild dose of warm water or "heat shock" stress in the laboratory and then transferred to elevated temperature conditions where we used the thermal outfall from power generation as a proxy to investigate the impacts of ocean warming. Shell growth, condition index, lipid content and profile and survival of oysters was impacted by elevated temperature in the field, with flat oysters being more impacted than Sydney rock oysters. Flat oysters grew faster than Sydney rock oysters at ambient temperature, but were more sensitive to elevated temperature. Early exposure to heat stress did little to ameliorate the negative effects of increased temperature, although the survival of heat shocked flat oysters was greater than non-heat shocked oysters. Further investigations are required to determine if early exposure to heat stress can act to inoculate oysters to future stress and overall enhance resilience of oysters to ocean warming.