sustainable source of protein for a growing population. But climate change poses a risk to the the industry. Increases in water temperature are expected to limit oyster growth and function, impact mortality rates and increase the spread and virulence of diseases.
This project explored the potential for conditioning oysters to withstand changes in temperature and disease. For one portion of the study, the researcher, Priya Shukla, exposed juvenile Olympia oysters (Ostrea lurida) to four different combinations of stressors: two temperatures (15°C and 21°C) and two tidal conditions (tide vs. no tide) for two weeks. The stress-hardened oysters were outplanted at Sacramento Landing in Tomales Bay for eight months. All of the oysters exposed to tide in the lab died, irrespective of temperature treatment. Oysters that experienced no tide at 21°C for two weeks had a 75% higher survival rate than oysters that experienced no tide and 15°C.
Shukla also exposed Pacific oysters (Magallana gigas) to varied temperature conditions. In 2021, oysters exposed to 21°C temperature for two weeks had lower mortality after an ostreid herpesvirus (OsHV-1) outbreak in Tomales Bay than those that experienced 16°C temperature during stress hardening. But this outcome did not repeat in 2022. This may be due to the fact that the disease occurred sooner in 2021 than in 2022 — roughly four weeks after stress hardening and outplanting of oysters, instead of eight weeks. Thus, in the latter year, the benefits of stress hardening may have worn off by the time the OsHV-1 outbreak occurred.
These findings suggest that briefly exposing oysters to warmer temperatures prior to outplanting them in the field could potentially reduce mortality. Ultimately, the resulting data can help shellfish aquaculture facilities determine whether conditioning oysters can improve their survival in the face of climate change.