Analysis of environmental factors influencing salinity patterns, oyster growth, and mortality in lower Breton Sound Estuary, Louisiana using 20 years of data

Freshwater inflow characteristics define estuarine functioning by delivering nutrients, sediments, and freshwater, which affect biological resources and ultimately system production. Using 20 years of water quality, weather, and oyster growth and mortality data from Breton Sound Estuary (BSE), Louisiana, we examined the relationship of riverine, weather, and tidal influence on estuarine salinity, and the relationship of salinity to oyster growth and mortality. Mississippi River discharge was found to be the most important factor determining salinity patterns over oyster grounds within lower portions of BSE, with increased river flow associated with lowered salinities, while easterly winds associated with increased salinity were less influential. These patterns were consistent throughout the year. Salinity and temperature (season) were found to critically control oyster growth and mortality, suggesting that seasonal changes to river discharge affecting water quality over the oyster grounds have profound impacts on oyster populations. The management of oyster reefs in estuaries (such as BSE) requires an understanding of how estuarine hydrodynamics and salinity are influenced by forcing factors such as winds, river flow, and by the volume, timing, and location of controlled releases of riverine water.