How have historic openings of the Bonnet Carré Spillway affected eastern oyster mortality?
What salinity conditions lead to ecological tipping points whereby oyster mortality is significantly increased due to freshwater inflow from the Bonnet Carré Spillway operations?
What salinity conditions lead to ecological tipping points whereby oyster mortality is significantly increased due to freshwater inflow from the Bonnet Carré Spillway operations?
The U.S. Army Corps of Engineers opens the Bonnet Carré Spillway to prevent the flooding of New Orleans, when Mississippi River flow exceeds 1.25 million cubic feet per second. While the operation of the Spillway represents a major flood relief for the people of New Orleans, the Mississippi Sound and Bight ecosystem is affected by the increased freshwater inflow, which shifts the salinity and temperature of the water, therefore affecting the suitability of the area for marine organisms. While Bonnet Carré Spillway operations are rare, occurring only 15 times since its construction in 1927, openings have increased in the past decade, with 5 since 2016 and the first double opening in 2019. As reported by Linhoss et al. (2023), Bonnet Carré operations can reduce the Mississippi Sound salinities by 25 ppt, creating uninhabitable situations for many marine fauna.
My current work seeks to evaluate how various Bonnet Carré Spillway operations affect water temperature and salinity in the Mississippi Sound, and how changes to these environmental variables affect the health of the eastern oyster (Crassostrea virginica). This work has multiple aspects, including physical models of changes to the salinity and temperatures in the Mississippi Sound, habitat suitability index modeling to evaluate how potential salinity and temperature changes will affect the suitability of oyster reefs for the oysters therein, and ecosystem modeling to evaluate how the combined changes in salinity, temperature, and habitat suitability affect the survivorship of oysters on reefs in the Mississippi Sound. By comparing the oyster survivorship under various Spillway operation scenarios, we hope to recommend changes of Bonnet Carré Spillway operations to mitigate harmful impacts to the Mississippi Sound estuary.
We have submitted this work for review and when the review process is completed, I am happy to share more about this work and our findings.
