Phytoplankton Population Dynamics at the Hawaii Ocean Time-series Station ALOHA

Lisa Campbell, Hector Nolla, Hong Bin Liu and Daniel Voulot

Abstract

The objectives of this research are to determine (1) the structure and composition of the phytoplankton community; (2) the contribution of the different algal populations to the total biomass; and (3) the annual variability in depth distribution and temporal patterns at Station ALOHA. We have provided the first detailed time-series data on the structure of the picophytplankton for the central North Pacific. Depth-integrated abundances of Prochlorococcus are higher at station ALOHA. Synechococcus are lower, and picoeukaryotes (< 3 µm diameter cells) are similar to reported results for Atlantic Ocean (Sargasso Sea) and Mediterranean Sea communities. Annual variablity is small for all three components, which is in contrast to observations in the Sargasso Sea. To examine the larger phytoplankton (3-20 µm diameter cells), we have modified the system (larger bore tubing and sample delivery tube) so that we can process aprroximately 10 ml of sample per minute. In contrast to the picoplankton, the larger eukaryotes are considerably more variable in terms of both cell number and estimated biomass (g C m^-2).