Comparative Analysis of Multiple Nesting Configurations in ROMS within COAWST Modeling Framework Focusing on Oyster Reefs in the Mississippi Sound

The oyster reef restoration process in the state of Mississippi has recently culminated because of its decline trends over the past one and a half decades. Two successive years of low salinity in 2018 and 2019 due to the excessive freshwater inflow via the Bonnet Carré spillway opening counteracted the restoration efforts. To make the oyster restoration efforts successful in the Mississippi Sound, more accurate salinity and temperature estimates should be provided within and around the proposed reef locations (Bay St. Louis & Pascagoula Bay) to understand the variability in a broader way. As the Mississippi Sound is a complex estuary, a high spatial resolution of numerical simulation is necessary to capture the physical variability of this region at smaller scales. To provide more accurate results, different configurations of nested simulation (both one-way and two-way) are run using two separate high-resolution (133m) nested grids focusing on the locations of experimental oyster leases; near Bay St. Louis, and near Pascagoula Bay. Significant spatial salinity differences occur among the different nested solutions where the salinity gradients are stronger between the estuarine and shelf water masses in the Pascagoula Bay. One-way and two-way solutions show less spatial salinity differences in the water column of Bay St. Louis nested solution because of the less salinity gradients between the estuarine and shelf water masses due to the high freshwater influx and confined communication between two water masses at Bay St. Louis area. Due to the exchange of information between the parent and nested grids in two-way solution, both solutions show higher correlation coefficients than the one-way solutions when compared with the observed tidal and subtidal salinity data at MDMR Station 9.