Cobalt oceanic distribution

Little is known of the oceanic distribution or speciation of cobalt, because very low concentrations (< 200 pM) make its determination difficult. Laboratory studies indicate that cobalt exists in seawater primarily as the cobalt (II) ion and as the carbonate complex. Organic complexes are not considered important. 

The oceanic distribution of cobalt is similar to that of manganese, although cobalt concentrations are 10-100 times smaller maximum concentrations are 100-300 pM in surface waters, decreasing to 10 pM at depths below 1000 m. As concentrations of cobalt in seawater are so low, it may become biolimiting in open ocean surface waters. 

Schutz, D. F., Turekian, K. K. The distribution of cobalt, nickel and silver in ocean water profiles around pacific antarctica. J. Geophys. Res. 70, 5519-5528 (1965 b). 

Cobalt, and sometimes cadmium, can substitute for zinc in many zinc enzymes such as CA, leading to complex interactions among the three metals in marine algae (Figure 5). The presence of cadmium in CA appears to explain its nutrient-like distribution in ocean waters (Figure 2(e)), and the identification of a unique Cd-CA enzyme in marine diatoms means that it functions as a micronutrient in these organisms. Cobalt also occurs in vitamin Bi2, an essential... 

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