The nitrate supply to the euphotic layer plays a key role in oceanic (and therefore global) carbon fluxes. Since ultraphytoplankton dominate these waters, their nitrate uptake arguably controls these processes. However, it is now believed that episodic nitrate pulses provide a significant fraction of the total annual primary productivity in the central gyres, yet the response of ultraphytoplankters to ecologically significant nitrate perturbations in nitrate concentration is likely to be a factor in species success of oceanic ultraphytoplankters. Drs Glover and Garside will characterize the kinetic response of oceanic algal and Synechococcus clones of ultraphytoplanton to ecologically significant (Nanomolar) increases in nitrate, using the chemiluminescent method. Experiments will involve measuring nitrate uptake, on a subsample of a nitrate-limited chemostat culture, exposed to different nitrate concentrations, but under the same temperature and light conditions as the parent culture. Their studies will contribute to understanding physical, chemical and physiological interactions that integrate to mediate 'new' nitrate-based production and ultimately control the oceans as a CO2 sink.
