"Saginaw Bay has always been one of the more productive regions of the Great Lakes system. At the present time, it is also one of the most modified. Excessive nutrient and conservative element loadings are factors which have led to severe perturbation of primary producer communities in the region. Because of the physical dynamics of the bay region, idealized dilution gradients are grossly modified by transport of water masses and their entrained chemical constituents, fauna and flora into, as well as away from, the Bay. However, there appears to be considerable selection among population components of the assemblages transported. For example, blue-green algae appear to be conserved in the Bay while diatoms are subjected to great losses. The major effort in this investigation was to provide data on phytoplankton biovolume that would support a model of processes occurring in Saginaw Bay. A method of estimating the actual viable fraction of the cell volumes of representatives of the various physiological groups of phytoplankton found in Saginaw Bay was developed, and polyphosphate body formation was studied. Results showed that substantial phytoplankton populations were exported from the Bay to Lake Huron. Under average wind conditions, most export occurred along the southern coast. These populations were then entrained in the general Lake Huron circulation and were spread down the Michigan coast southward from the Bay. Under certain advective conditions, however, phytoplankton were discharged from the Bay either to the north or directly offshore. Cytological analysis showed that many species sequestered phosphorus in excess of their immediate physiological needs, in the form of polyphosphate bodies. Populations exported from the Bay also contained these polyphosphate bodies. Analysis of the polyphosphate bodies showed that significant quantities of certain toxic metals, notably lead, were incorporated into these inclusions. Analysis of the relationship of total phytoplankton cell volume to protoplasmic constituent volume showed that crude cell volume measurements furnished a poor estimate of actual living biomass in many populations. It was concluded that more refined techniques are required to correctly convert estimates of cell number to estimates of biomass."