Riverine Iron and Estuarine Systems

Iron (Fe) is an essential micronutrient often limiting to primary producers. Iron isotopic compositions have become a useful oceanographic tool providing more insight into the sources of Fe to the global ocean. However, the isotopic compositions of riverine-derived Fe vary significantly based on location, chemical composition, organic matter and seasonality. We propose to establish the Iron isotopic compositions endmembers of five key rivers (Hillsborough, Alafia, Manatee, Peace and Caloosahatchee rivers), sample three corresponding estuaries (Tampa Bay, Charlotte Harbor, Caloosahatchee estuary), and supplement field studies with quantitative mixing experiments. Coordination with a recently funded NSF West Florida Shelf study, provides a unique opportunity to close a key gap in knowledge by determining processes that modify riverine derived dFe through an estuary, over the shelf to offshore surface waters. Understanding the mechanisms by which micronutrients such as Fe, enter and cycle through the dynamic WFS Shelf greatly increases our understanding of key processes controlling primary production and Harmful Algal Bloom events. Increasing spatial and temporal resolution of high-quality Iron isotopic compositions riverine endmembers will not only improve the global data set and biogeochemical model predictions, but it will help us provide more insight into the sources of

bioavailable Fe to the WFS.