Concentration of total dissolvable and total iron, manganese, cobalt and nickel in the water column at 5 sites along a water depth transect in the Gulf of Mexico (Louisiana continental shelf)

The concentration of Fe in water column samples was determined by flow injection chemiluminescence with preconcentration detection. Total dissolvable Fe concentrations were determined 3 months after sample collection. All samples per station were analyzed in triplicate in the same run. The blank of acidified ultrapure water (pH = 1.8) was 32 ± 39 pmol L−1 (n = 194). The average limit of detection (LOD), calculated as the standard deviation of the analysis of oligotrophic seawater with known trace metal concentrations, multiplied by 3, was 86 ± 120 pmol L−1 (n = 19). The concentrations of Co, Mn, and Ni were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS; Nexion ICP-MS (Perkin Elmer)) after pre-concentration with an SC-DX SeaFAST S2 (Elemental Scientific). Total dissolvable Co, Mn, and Ni were determined 7 months after sample collection. The LOD values for Co, Mn, and Ni were 0.027 ± 0.004, 0.11 ± 0.024, and 0.99 ± 0.12 nmol L−1 (n=5), respectively, and the values of the oligotrophic seawater were 0.77 ± 0.9, 0.9 ± 0.5, and 4.41 ± 0.52 nmol L−1 (n=40), respectively.