P.I.: Goericke Proposal #: 95- 04117 PROJECT ABSTRACT To understand the controls of primary production in the world ocean, variations of phytoplankton biomass and primary production must be understood as a function of physical, chemical and biological parameters. Ideally, one would determine primary production as the sum of the products of phytoplankton taxon specific biomass and growth rates. Although this approach is currently not possible, phytoplankton biomass and growth rates can be measured using the chlorophyll-labeling method, which as introduced a decade ago. Taxon specific growth rates can, in principle, also be determined from the 14C labeling of carotenoids. However, these potentially powerful methods have been used on a limited basis because a mechanical understanding of what is being measured was lacking. This research will study the 14C labeling kinetics of chlorophyll a and carotenoids in nitrogen limited continuous cultures of microalgae grown under constant light to extend previous research to other carotenoids, groups of algae, and conditions of nutrient-limited growth. The study will also determine pigment-labeling kinetics in algae grown under a diel photocycle and algae subject to growth irradiance changes to assess the limitations of the method when it is performed under conditions of uneven growth. The results of this study will aid other members of the research community in the interpretation of the pigment labeling experiments.
