A conservative data set was chosen to describe ecosystem behavior; total zooplankton, chlorophyll a, ammonia, nitrite, plus nitrate, phosphate and silicate. These variables were measured weekly in the microcosms, as well as in a field survey of Narragansett Bay in 1972-73; thus a comparison data set was available. Two types of statistical techniques were used to explore the question of divergence among replicate microcosms and treatment groups (including the bay stations as treatment groups): Multiple Discriminant Analysis and Distance Statistics. The first was used to explore the major axes of variation between replicate tanks and bay stations. Distance statistics were used to describe the divergence of replicate tanks and treatment groups as a function of time.