The eukaryotic ultraplankton (1-6 + um) is at times the most signigicant component of the photosynthetic plankton, both in terms of biomass and primary productivity, especially in the deep chlorophyll maximum (ca. 100 m depth). The species comprising it have been studied very little for two reasons; besides their small size, their fragility makes most preserve poorly for routine observation, and their sensitivity has until recently made isolation into culture exceedingly difficult. Our ultraplankton collection now contains some 200 clones in unialgal or axenic culture. With collaborators we are studying (1) morphology and ultrastructure by light microscopy, SEM and TEM, and (2) photosynthetic pigment suites by HPLC and techniques of carotenoid chemistry. The results will assist in placing the organisms taxonomically and undoubtedly will result in new taxa, new taxonomic criteria, and possibly major revision of some higher systematic levels. We also study nutrition of the clones in culture. Some have heterotrophic or phagotrophic capabilities. Requirements for trace elements - Fe, Mn, Zn, Se - will be compared to the requirements of known oceanic and neritic phytoplankton species by growth studies under defined conditions. These studies, together with those being carried out by other groups on photosynthetic behavior, other physiological properties, grazing, etc. will give us much better understanding of the ecology of this important flora, now available for study.
