FE, ZN, MN AND N TRANSFER BETWEEN SIZE CLASSES IN A COASTAL PHYTOPLANKTON COMMUNITY - TRACE-METAL AND MAJOR NUTRIENT RECYCLING COMPARED

Experiments were performed to investigate transfer of Fe-59, Zn-65, Mn -54, and N-15 from labeled cyanobacteria to the large (> 8 mu m or >5 mu m) phytoplankton size class from Monterey Bay, California. Transfer of metal isotope activity was measured from and into total (for all i sotopes) and intracellular (Fe-59 only) pools. Results demonstrated ra pid and efficient transfer of nitrogen to the large phytoplankton size class; intracellular Fe-59 was transferred into the intracellular and total pools of the > 8 mu m phytoplankton size class 70% and 130% as efficiently as nitrogen, respectively. Zn-65 and Mn-54 were transferre d between size classes 48% and 23% as efficiently as N. Extracellular Fe-59 and Zn-65 from the added cyanobacteria also appeared quickly in the large size fraction, although most of the Fe transfer appeared to be the result of surface adsorption rather than biological uptake. The se data are discussed in relation to the biological recycling efficien cies of the four elements and the resulting implications for biogeoche mical cycling of trace and major nutrient elements.