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Research Day Entry

Seasonal variability in dissolved iron and dissolved organic matter in the Connecticut River

Laura Logozzo
Iron is a limiting nutrient in the open ocean. Rivers can be sources of dissolved iron to oceans and coastal zones if iron is bound to dissolved organic matter (DOM). However, the seasonality of dissolved iron and DOM in rivers is poorly categorized, making riverine iron export estimates uncertain. We sampled 5 sites along the Connecticut River mainstem, bi-weekly. We found that iron and DOM co-varied in the summer, fall, and winter, and that iron concentrations were dependent on DOM concentration and source. Iron concentrations were close to 0 when river discharge was low, particularly in the summer, indicating either iron uptake by primary production or a lower contribution of terrestrial DOM, which preferentially binds iron. Iron concentrations were greatest in the fall, when DOC concentrations were highest and there was a higher contribution of more degraded DOM. This demonstrates clear seasonal patterns of riverine iron concentrations.