Estimating the Distribution and Production of Microplankton in a Coastal Upwelling Front from the Cellular Content of Guanosine-5 Triphosphate and Adenosine-5 Triphosphate

This thesis examines the distribution and production of micro-organisms within a coastal upwelling front located off Pt. Sur, California. Underway measurements of adenosine-5'-triphosphate (ATP) and pigment fluorescence (principally chlorophyll a) were used to estimate the amount of living biomass present at 2.5 m. Specific and absolute productivity were measured by the nucleotide ratio of guanosine-5'-triphosphate (GTP) to ATP and GTP, respectively. The highest concentration of biomass associated with the highest rate of absolute productivity was preferentially located in the strong thermo-nutrient gradient in the warmer stratified water at the equatorward edge of the feature. The measurement of specific productivity using the GTP to ATP ratio was significantly correlated with assimilation numbers (productivity index), lending support to the hypothesis that this ratio is a good indicator of specific community productivity in microplankton (principally phytoplankton). No correlation existed between the GTP concentration which was enzymatically determined, and the concentration of GTP which was inferred from the calculated values of delta ATP. This finding indicates that delta ATP is not a good estimator of GTP in community assemblages of microplankton.