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

We investigated biological Fe recycling in plankton communities from t wo contrasting marine ecosystems, the equatorial Pacific and Monterey Bay, California. Our experiments involved addition of cultured cyanoba cteria and diatoms labeled with Fe radiotracer to natural plankton com munities. 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 bo th environments and from large diatoms to indigenOus small cells in th e equatorial Pacific. MicroautoradiograPhY and Ti washing verified tha t transfer occurred from and into intracellular fractions in Monterey Bay experiments, although substantial amounts of transferred Fe were a lso found to be surface-adsorbed or associated with detritus. We argue that, as is the case for N, recycling of cellular Fe to support regen erated production could be an important component of marine ecosystem dynamics, especially in areas low in Fe.