The photosynthetic ultraphytoplankton dominate ocean systems, both in terms of primary productivity and biomass, especially in stratified waters. However, the eukaryotic ultraplankton are only poorly known. This lack of basic information probably results from their small size, fragility, and resistance to culturing efforts. General studies of pigments in diverse oceanic systems reveal several abundant pigments which undoubtedly are from the eukaryotic ultraplankton and they undoubtedly will be of utility in classifying and identifying the taxa. However, there has been no systematic attempt to correlate these pigments with the taxa---a result of lack of species definition. It is unclear whether the few recorded instances are characteristic of the oligotrophic systems. The PIs propose to characterize oceanic ultraplankton populations through the seasons and at a variety of stations in the Atlantic and Pacific oceans. They will use ultrastructural analyses of cultured specimens to provide reference materials and correlate those morphological entities with their pigment- signatures. The resultant information will provide valuable information for studies on distribution, physiological ecology, and systematics of the oceanic ultraphytoplankton.
