IRON AND REGENERATED PRODUCTION - EVIDENCE FOR BIOLOGICAL IRON RECYCLING IN 2 MARINE ENVIRONMENTS

We investigated biological Fe recycling in plankton communities from two contrasting marine ecosystems, the equatorial Pacific and Monterey Bay, California. Our experiments involved addition of cultured cyanobacteria and diatoms labeled with Fe radiotracer to natural plankton communities. Transfer of label into the natural community was followed by size fractionation and microautoradiography, and intracellular Fe was determined with titanium wash techniques. We documented the transfer of labeled Fe from added cyanobacteria to indigenous large cells in both environments and from large diatoms to indigenOus small cells in the equatorial Pacific. MicroautoradiograPhY and Ti washing verified that transfer occurred from and into intracellular fractions in Monterey Bay experiments, although substantial amounts of transferred Fe were also found to be surface-adsorbed or associated with detritus. We argue that, as is the case for N, recycling of cellular Fe to support regenerated production could be an important component of marine ecosystem dynamics, especially in areas low in Fe.