RESULTS

Dissolved Mn²⁺ concentrations range between 0.1 and 26.5 µM (Table T1; Fig. F1) and average 1.8, 3.3, 3.8, and 1.0 µM at Sites 1119, 1122, 1123, and 1125, respectively. Thus, Mn²⁺ concentrations are relatively high at the deep sites (1122 and 1123) and relatively low at the shallow sites (1119 and 1125). This observation may reflect higher inputs of reducible solid Mn phases at the deeper locations. There is an overall positive correlation between dissolved Mn²⁺ and dissolved SO₄^2- concentrations (Fig. F1). Because SO₄^2- reduction increases alkalinity, it is probable that Mn²⁺ profiles are strongly influenced by authigenic carbonate precipitation and incorporation of Mn.