Importance of Picoplankton in Lake Superior

摘要: In Lake Superior, approximately 50% of total primary production is attributable to phytoplankton that pass through a 3-μm screen. The <3-μm size class dominated by eukaryotic flagellates, nonmotile cells (1 μm), and chroococcoid cyanobacteria. Approximately 20% orange autofluorescent cyanobacteria (mean size = 0.7 μm) as determined fractionation track autoradiography. These small prokaryotes exhibited abundances 42 000 56 000 cells∙ml−1, maximum photosynthetic rates 7 6 fg∙cell−1∙h−1, growth 1.5 0.8∙d−1 in the epilimnion hypolimnion, respectively. A significant portion this picoplankton (<1 μm) may be consumed heterotrophic protozoans "microbial loop."