Oxygen isotope records of the Australian flat oyster (Ostrea angasi) as a potential temperature archive

Abstract

The response of the oxygen isotope ratio ( δ 18 O) in shells of the Australian native flat oyster Ostrea angasi to changes in water temperature has been assessed using growth experiments conducted for one year at two locations on the east coast of Australia. The analysed δ 18 O of the oyster shells ( δ 18 O shell ) closely follows the predicted oyster shell δ 18 O constructed from measured δ 18 O in the water ( δ 18 O water ) and water temperature. Influxes of freshwater that occur in the estuarine habitats of O. angasi can modify the δ 18 O water , and consequently δ 18 O shell . Salinity fluctuations can also cause interruptions to shell growth in this species. This can cause overestimated temperatures in O. angasi δ 18 O shell temperature reconstructions. A δ 18 O shell –temperature calibration was established for O. angasi , yielding the relationship: T°C = 13.97 − (3.57 δ 18 O shell − δ 18 O water ) + (0.17 δ 18 O shell − δ 18 O water ) 2 , n = 79, R 2 = 0.79, which, within the experimental uncertainties of the data, is similar to other published biogenic carbonate paleotemperature equations. • The δ 18 O shell of the Australian oyster Ostrea angasi records the ambient water temperature. • Changes in the δ 18 O water in the oysters’ estuarine habitat will influence the δ 18 O shell . • A δ 18 O shell –temperature calibration specific to Ostrea angasi -specific was developed.