Mesoscale Cyclonic Eddies Formed Near the Hawaiian Islands will be utilized to study the effects of upwelling events on the productivity, composition, biomass, and physiology of open-ocean phytoplankton populations. Recent technical and methodological advances will be utilized to more accurately determine the ratio of new production to total production (f-ratio) and the temporal and spatial variability of that ratio in the open ocean. Both simple empirical models and more sophisticated compartmental models will be tested for their ability to describe and explain observed f-ratio variations. Estimates of new production will be obtained using a recently developed nitrate analysis method with a precision of +/- 2nM. Total production will be estimated from the incorporation of C-14 labeled inorganic carbon into protein. This experimental approach will eliminate many of the potential artifacts and problems associated with traditional f-ratio studies, including perturbations caused by the addition of non- tracer amounts of N-15, isotope dilution of the substrate pool, difficulty in measuring ambient substrate concentrations, the need to measure uptake of at least three forms of dissolved N, and the fact that bacteria may account for a significant fraction of the uptake of ammonium. The biological productivity of the ocean varies geographically to a great degree. In mid-basin subtropical areas such as thevicinity of the Hawaiian Islands, production is typically relatively low. However, physical features of the local waters such as the circular eddies found to the west of the islands can enhance productivity by increasing the supply of nutrients for plant growth to surface waters. Laws and Bienfang will use state of the art techniques to measure these variations in biological production and relate it to the structure of the planktonic community. They will make sensitive measurements of new production, a parameter that is critical in estimating the flux of organic material from surface waters and its availability for harvestable resources. Conducting the studies in an area where oceanic eddies are found will provide a wide range of biological oceanographic conditions likely to be found in the open ocean.
