Cobalamin and Thiamine in Long Island Sound: Patterns of Distribution and Ecological Significance1

Cobalamin occurs in surface waters of Long Island Sound at high levels (to 16 µµg/ml) during the winter, falling markedly with the late winter diatom bloom and rising during the summer with temperature. The pattern of cobalamin and PO4‐P concentrations are similar, both nutrients reflecting but not limiting phytoplankton growth. Thiamine is present only in barely detectable amounts in the main body of the Sound. Data suggest that thiamine, but not cobalamin, may be mainly derived from land drainage.