Characterizing Manganese Cycling During Estuarine Mixing

Abstract

Manganese (Mn) is a trace element essential for life. In the environment, it can exist in three states (Mn(II, III, IV)), with Mn(II) being dissolved, Mn(IV) being particulate, and Mn(III) being particulate unless stabilized by organic molecules known as ligands. This project aimed to understand how Mn cycles between its three states during mixing of the Mississippi River and the Gulf of Mexico through a mixing experiment designed to mimic the salinity gradient. The proportion of dissolved Mn(III) may have been influenced by the salinity gradient, although rates of ligand promoted reduction of MnOx did not vary along it. These have broader implications for how the transition from freshwater to seawater impacts the transport of Mn, and establish a better understanding of how the salinity gradient influences the phase of Mn. Having better insight into how Mn cycles in the Mississippi River delta is important because of the broader implications it has for the chemistry of the Northern Gulf of Mexico