Prochlorococcus and Synechococcus contribution to primary production in the equatorial Pacific Ocean (2012)
Undergraduate: Kelly Speare
Faculty Advisor: Barbara MacGregor
Department: Biology
In this study I investigate the distribution of Prochlorococcus (PRO) and Synechococcus (SYN) over a latitudinal transect of the central equatorial Pacific Ocean. The study tests the hypothesis that PRO and SYN are the major contributors to primary production in the oligotrophic North Pacific Subtropical Gyre and that they contribute less to overall primary production in the region of equatorial upwelling where nutrients are abundant. It also tests the hypothesis that although PRO and SYN are abundant in nutrient poor waters, cell densities increase with nutrient availability. Chlorophyll a concentration is used as a proxy for primary production, and was fractionated into total chlorophyll a concentration and chlorophyll a from organisms <5.0µm. The contribution of organisms <5.0µm, such as PRO and SYN, had variable contribution to total chlorophyll a, but results were not consistent with the hypothesis that they contribute the most to chlorophyll a concentration in oligotrophic waters. In other regions, however, contributions to total chlorophyll a were in excess of 75% in waters with elevated nitrate availability. The results support the hypothesis that PRO and SYN cell densities increase with nutrient availability. However, increased nutrient availability did not necessarily denote areas of increased cell densities.