R/FISH-107

Strategic focus area:

Description:

Acidification due to excessive respiration resulting from eutrophication as well as increasing atmospheric CO2 is predicted to have dramatic negative effects on the Eastern oyster (Crassostrea virginica), a species of high economic, ecological, and cultural importance in Maryland. Initial studies have shown that oysters are negatively affected over the short term by severe acidification, but investigations of the long-term responses to acidification are lacking. Understanding how oysters respond to varying levels of acidification over longer timescales, especially in the context of co-occurring stressors, such as hypoxia, is of vital importance for improving oyster fisheries and the success of restoration efforts, as well as for guiding aquaculture expansion. 

Preliminary work has indicated that juvenile oysters may be able to acclimate over a period of months after initial exposures to acidification and hypoxia, though the long term ramifications of these exposures are unknown. If it turns out that oysters are able to tolerate stressors over longer time periods, new areas of Chesapeake Bay could potentially be opened to aquaculture and restoration projects. By testing various severities and combinations of these stressors, we can determine thresholds for long-term success in oysters and gain a deeper and more nuanced understanding of how they might respond to climate change in coming decades. 

To investigate the capacity for oysters to acclimate to acidification and hypoxia, we will settle larvae in the laboratory and raise them under six treatments along a gradient of these stressors for six weeks. We will record a suite of physiological and morphological metrics, and then outplant the oysters to sites around Chesapeake Bay. Oysters will be retrieved after 3 months to assess their condition, then replaced at field sites to overwinter. A third round of measurements will be taken in June of Year 2, followed by a final round in October of that year after oysters have spent a second summer in field conditions. Additionally during Year 2, we will subject a second set of juveniles to acidification and hypoxia in a factorial design in the laboratory, and then redistribute them among laboratory treatments. Redistributing oysters in this manner will allow us to determine if early exposure to a specific stressor or combination of stressors confers a benefit or a drawback to oysters when subsequently exposed to different stressors. 

These multiple measures of how oysters exposed to stress as juveniles respond to stress during development will help inform the siting of restoration projects, aquaculture leases, and oyster grow-out programs. The information we gather will be distributed to audiences of interested stakeholders, and should contribute to success of restoration projects and aquaculture.