Wild and farm Eastern oyster (Crassostrea virginica) contributions to improved water quality in the mid-Atlantic: contemporary and future climate estimates
Creators: name: Barr, Janine Meghan
Publisher: name: No Publisher Supplied
Year: 2022

description: Globally it is estimated that 85% of oyster reef ecosystems have been lost over the past 130 years as a result of overharvesting, changes in freshwater inflows, alterations to shorelines, disease, and other factors. This decline has resulted in a loss of the ecosystem services oysters provide such as water quality improvements. Restoration of natural oyster reefs has been a common solution, but research suggests oyster aquaculture could be providing equivalent or greater water quality benefits than reefs. However, the scale at which oyster farms provide important ecosystem services is not adequately known. Furthermore, there is a lack of data concerning site-specific effects of changes in salinity on oyster filtration. Oysters are generally resilient to changes in salinity, but prolonged exposure to low salinity conditions have caused severe mortality events in oyster populations. Low salinity stress will likely increase with climate change as the frequency and intensity of extreme rainfall events increases across the mid-Atlantic. This thesis aims to address the aforementioned concerns by (1) quantifying farm-specific year-round Eastern oyster (Crassostrea virginica) filtration at three oyster farms in the mid-Atlantic and (2) assessing the effects of decreased salinity on the filtration services provided by a wild oyster bed and an oyster farm in Delaware Bay, New Jersey. Field experiments were conducted seasonally using a flow-through filtration chamber with ambient water to calculate individual oyster filtration physiology. The experiments discussed in Chapter 1 provide a robust dataset of oyster feeding behavior observed under natural conditions across oyster farms. The results show oyster filtration physiology differed among locations and through the year. Collectively, an increase in salinity and temperature was associated with an increase in oyster physiological activity across all farms, but physiological activity at each farm was associated with a different suite of environmental variables (including total particulate matter and the organic content of seston). These data may be used in a broader framework to inform development of nutrient management strategies in the mid-Atlantic. The experiments discussed in Chapter 2 estimate the impacts of seasonal climatic stress (i.e., increased extreme precipitation events) on wild and farm oyster filtration. The results show wild and farm oyster populations provide reduced water quality benefits during a Hurricane Sandy scale salinity disturbance occurring between the spring and the late-fall. Individual wild and farm oyster responses to the low salinity conditions were varied highlighting the importance of gathering oyster- and site-specific feeding behavior data. These data may be used to inform proactive, long-term management of wild and farm oyster populations in the region to achieve water quality and oyster stock goals. Together, these chapters highlight the utility of wild and farm oysters as a nature-based water quality management tool and the importance of making conservative estimates of ecological filtration to account for days of low oyster physiological activity triggered by possible environmental stressors.