Eight productivity experiments performed in the York River, Virginia, during the summer of 1963 are described. A factorial design was used in which water samples from seven depths were suspended throughout the water column to obtain data on gross production, respiration, and net production as functions of collection and suspension depths. Characteristics of these functions, represented as response surfaces, are described in relation to hydrography and phytoplankton species composition. It is shown that levels of production and respiration cannot be inferred from data on cell abundance and species composition since the latter information does not express dynamic states of the component populations. In a subsequent paper based on the present data average photosynthesis, respiration, and net production per cell of the principal species in mixed samples will be estimated to develop information about state changes of specific populations during succession.