Variation in Dissolved Organic Matter, Trace Metals, and Acidification Parameters in the Western Mississippi Sound

Sankar, M. S., Dash, P., Lu, Y., Mercer, A., Arslan, Z., Sanders, S. L., Wickramarathna, S., Ragland, R., Chen, S., & Moorhead, R. J. (2019). Variation in Dissolved Organic Matter, Trace Metals, and Acidification Parameters in the Western Mississippi Sound. CERF-2019. Coastal and Estuarine Research Federation (CERF)-2019, Mobile, Alabama.

The total amount of oysters harvested in the Mississippi Sound has declined by 85.71% over the last 13 years. The objective of this study was to assess the influence of water quality on the oysters, specifically the temporal changes in dissolved organic matter (DOM), trace elements, and ocean acidification parameters over the largest oyster bed in the western Mississippi Sound. To evaluate water quality, water samples from 52 locations were collected over the oyster bed from March to December 2018. The results from 46 locations for which the water samples have been analyzed so far revealed the presence of two terrestrial humic-like, two bacterial protein-like, and a photochemically originated DOM over the oyster bed from March to July. Additionally, the analytical results indicated a steady increase in the average concentrations of arsenic, uranium, iron, and zinc, while the average concentrations of manganese, copper, and mercury remained the same. On the other hand, the concentrations of lead decreased on average. Furthermore, the ocean acidification parameters such as pH, dissolved inorganic carbon, and total alkalinity also showed an increasing trend over the oyster reef from March to July. Statistical analysis revealed an increase in the partial pressure of CO2 and low pH in waters during March and May due to a higher rate of photodegradation of terrestrial humic-like DOM. The DIC, TA, aragonite saturation states, and calcite saturation states showed an increasing trend along with total dissolved solids (TDS) and suspended particulate matter (SPM) during June and July, which suggested a highly alkaline river input. Additionally, the association of arsenic, uranium, and iron along with SPM and TDS indicated terrestrial sources. Overall, the present research suggested that photodegradation of DOM along with the riverine input influence the water quality over the oyster beds in the western Mississippi Sound significantly.