Manganese in the Western North Atlantic Ocean

Dissolved and total dissolvable manganese concentrations have been measured at four stations in the western North Atlantic Ocean. Total dissolvable manganese concentrations are high in surface waters, decrease to uniformly low levels throughout the bulk of the water column, and increase in the bottom nepheloid layer. Dissolved Mn (Mn_d) concentrations follow the total dissolvable concentrations throughout the surface and deep waters but do not increase in the near-bottom waters.Deep water concentrations of Mn_d decrease from 30 ng l^?1 in the Newfoundland Basin to 20 ng l^?1 in the Sargasso Sea. This change and other features of the deep water distribution of dissolved manganese could be associated with the slow oxidation of Mn²⁺ to MnO₂. There is also evidence at one station of scavenging of manganese from the dissolved phase in the near-bottom layer which may again be related to the kinetics of manganese oxidation.