Projection of Freshwater Diversion Impacts under Relative Sea-Level Rise on Louisiana Oysters Using a Coupled Hydrodynamic-Water Quality-Oyster Population Model
A coupled hydrodynamic, water quality and oyster population model was integrated with field measurements to assess the impacts of river diversion projects on oyster population size, growth rates and total production, and to project those impacts on oyster production under different scenarios of Relative Sea-Level Rise (RSLR) in the Breton Sound Estuary, an important oyster production area in Louisiana. Through the Louisiana Sea Grant, results were extended to both the stakeholders involved in oyster production and the managers of wetland restoration in coastal Louisiana.
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- Develop a coupled hydrodynamic, water quality and oyster population model
- Examine the effects of Mississippi River diversions and RSLR on the spatial and temporal variability of eastern oyster population dynamics in coastal Louisiana, using an integrated spatial modeling approach.
In a rapidly changing coastal environment, knowing when and where appropriate conditions will exist for productive oyster aquaculture is critical for proper management of the industry.
- We simulated the spatial and temporal patterns of salinity, TSS, and Chl-a in the Breton Sound Estuary (BSE) using the water quality model (Delft3D-WAQ) in the Delft3D model suite, supplied with data from the hydrodynamic model (Delft3D-FLOW) in the Delft3D model suite. The input for the hydrodynamic model (Delft3D-FLOW) includes tides, river discharge, and atmospheric pressure. TheDelft3D-FLOW model for BSE has been set up, calibrated, and validated using 2012 Hurricane Isaac data in a previous study (Hu and others 2015).The Delft3D-FLOWand Delft3d-WAQ models were integrated by a spatial and time coupling algorithm that allows for the changes (i.e., aggregation) of spatial resolution and timestep within the Delft3D-WAQ model.
- We applied the post-settlement oyster population dynamic model (Wang and others 2008) with necessary modifications for the specific physical and biological conditions of BSE to simulate the growth, respiration, reproduction, and mortality of the benthic phase of the oysters’ life history from newly settled juvenile through adulthood under various environmental conditions. The forcing functions of the model include estuary salinity, temperature, turbidity, food, and current velocity.
- We selected two diversion flow scenarios; low (142 m3 s-s) and a high (7080 m3 s-s) flow at the Caernarvon Freshwater Diversion structure in the vicinity of Braithwaite. Similarly, we chose two RSLR scenarios for BSE the next 50 years; low (0.38 m), and high (1.44 m). We ran the model using a full factorial model of all individual and combined diversion (low, high) and RSLR (low, high) scenarios along with the baseline year (2009).
- Hu, K., Chen, Q., and Wang, H., 2015, A numerical study of vegetation impact on reducing storm surge by wetlands in a semi-enclosed estuary: Coastal Engineering, v. 95, p. 66–76.
- Wang, H., Huang, W., Harwell, M.A., Edmiston, L., Johnson, E., Hsieh, P., Milla, K., Christensen, J., Stewart, J., and Liu, X., 2008, Modeling oyster growth rate by coupling oyster population and hydrodynamic models for Apalachicola Bay Florida, USA: Ecological Modeling, v. 211, p. 77–89.
- Wang, H., Chen, Q., Hu, K., and LaPeyre, M.A., 2017, A modeling study of the impacts of Mississippi River diversion and sea-level rise on water quality of a deltaic estuary: Estuaries and Coasts, v. 40, p. 1028-1054, doi:10.1007/s12237-016-0197-7.
- Wang, H., Chen, Q., LaPeyre, M., Hu, K., LaPeyre, J., and Lively, J., 2017, Predicting the impacts of Mississippi River diversion and sea-level rise on eastern oyster growth rate and production. Ecological Modeling, v. 352, p. 40-53.