Iron in Maine coastal waters; seasonal variation and its apparent correlation with a dinoflagellate bloom

During 1975, 12 km south of Boothbay Harbor, soluble iron concentrations in the first 20 m of water were three times greater in October and November than in August and September, while particulate iron concentrations only increased transiently before the fall bloom. Nutrient enrichment experiments and chlorophyll a : cytochrome f 1 ratios indicated that low iron concentrations limited phytoplankton populations. In August 1976, 1–4 km from Monhegan Island, increased iron concentrations from land runoff preceded a dinoflagellate bloom.