The structure of the phytoplankton community in the North Water Polynya will be studied during the summer of 1998. The North Water is a predictable, recurrent area of open water situated in northern Baffin Bay, which is ice-free beginning in March. The taxonomy of diatoms and flagellates from Baffin Bay has been studied in previous decades, and primary production was measured at a few stations in the southern area of the North Water in the 1970's. Other than these studies and a 48 hour study in May 1991, little is known of the biological oceanography of this area which is very rich in marine mammals and birds. The proposed project will quantify, using epifluorescence microscopy, the algal populations belonging to various groups, such as diatoms, autotrophic dinoflagellates and other autotrophic flagellates in terms of cell concentration and biomass (as carbon) of individual taxa. The project will be part of the International North Water Polynya Study comprising physical, chemical and biological studies of the area, and samples will be collected in conjunction with the Canadian study of primary production. The relation between phytoplankton community structure and physical, chemical and biological parameters will be examined. Conclusions will be drawn as to which environmental conditions lead to removal of carbon to the benthos, and which lead to carbon remaining in the upper layers. In collaboration with other investigators, the consequences of a possible future warming of the North Water will be explored, especially the effects of existing food chains.