Throughout the summer of 1978, the sinking rates of phytoplankton within the Controlled Experimental Ecosystems (CEE's) were monitored using a technique based upon measurement of the transit time of radioactively (14C) labeled cells. The experimental framework of FOODWEB 1 offered an unprecedented opportunity to document the sinking rates of heterogeneous phytoplankton of diverse taxonomic composition, growing under a variety of nutrient regimes; the absence of advective exchange in the CEE's provided knowledge of the preconditioning history of the phytoplankton sampled at any given time.