Assessing the chemical speciation and bioavailability of iron regenerated by marine zooplankton

Bigelow Laboratory For Ocean Sciences, East Boothbay ME

Investigators

Abstract

Iron (Fe) is a required, but often limiting nutrient, in the upper ocean. Sources of Fe include external inputs, as well an in situ regeneration due to the rapid recycling of Fe in surface waters through biological uptake and regeneration, including via zooplankton grazing. Digestion of phytoplankton biomass in zooplankton guts is expected to result in chemical redox and speciation changes which will affect Fe bioavailability, but this recycling process remains understudied. The current project will examine this topic through a series of laboratory and field investigations which will probe the consequences of grazing on chemical speciation and bioavailability. The studies will investigate the pH and redox state in the digestive vacuole/guts of different zooplankton, and examine how prey ? grazer dynamics influences the speciation of regenerated Fe, and its bioavailability to cultures of model phytoplankton. Field experiments will also examine Fe regeneration, speciation and bioavailability using natural prey - grazer assemblages from coastal and open ocean waters during cruises funded through other programs. The project will educate and train students and scientists at the high school, undergraduate and post-doctoral levels at institutions in Maine, and through programs at the Bigelow Marine Lab. Undergraduates will be involved in studies through the Bigelow REU program. Overall, the project will provide important information on the sources and pathways of iron uptake into marine microbes and the factors influencing bioavailability in marine waters by focusing on one aspect of this important research area.