Importance of Picoplankton in Lake Superior

Abstract
In Lake Superior, approximately 50% of total primary production is attributable to phytoplankton that pass through a 3-μm screen. The −1, maximum photosynthetic rates of 7 and 6 fg∙cell−1∙h−1, and growth rates of 1.5 and 0.8∙d−1 in the epilimnion and hypolimnion, respectively. A significant portion of this picoplankton (<1 μm) production may be consumed by heterotrophic protozoans in a "microbial loop."