EFFECTS OF NUTRIENTS AND SALINITY ON WATER QUALITY AND ECOSYSTEM OF THE WESTERN MISSISSIPPI SOUND

Coastal environments are exposed to human and natural activities, which negatively impact water quality. Surface water samples were collected from a human-crewed boat, and surface water quality data was collected using a novel autonomous surface vessel (ASV) in the Western Mississippi Sound (WMS) from 29 and 19 stations in the summer of 2021 and 2022, respectively. The Nutrient, salinity, and chl-a data in these samples were analyzed and compared. The salinity varied between 2.4 PSU and 22.9 PSU, suggesting a temporal variation in freshwater contributions from the Mississippi River, Pearl River, St. Louis Bay outflow, Biloxi River, Pascagoula River, and Mobile Bay, following precipitation events leading to nutrient transport and dilution of the salinity in the WMS. Nutrient concentrations were 0.11 - 660 µg/L and 74 - 151 µg/L for nitrate in summer 2021 and fall 2022, respectively, 54.13 - 85.47 µg/L and 74 - 113 µg/L for phosphate in summer 2021 and fall 2022, respectively. Ammonium ranged between 0.00 - 660 µg/L and 4.15 - 139 µg/L in the summer 2021 and fall of 2022, respectively. Based on the ASV data, salinity is inversely related to chl-a. Plots of salinity against chl-a show a relative increase in the concentration of chl-a with a decrease in salinity, which can be attributed to freshwater-laden nutrients causing an increase in phytoplankton biomass. Plots of salinity against nutrients show negative correlations in the summer of 2021 and 2022, except ammonium, in the summer of 2022. Future studies would address the relationship between nutrients and trace metals, and their impacts on the Mississippi Sound, to estimate pollution status and possible remediation strategies.