Phytoplankton species structure in the central North Pacific, 1973-1996: variability and persistence

Acquisition of recent phytoplankton samples from JGOFS' station ALOHA and the Climax area prompted updating and re-evaluation of 23 years of floristic data from the summer central North Pacific environment. Recurrent group analysis clearly shows the dichotomy between shallow and deep associations. A new finding is that the deep flora consists of two related groups of species whose abundance centers are vertically displaced from one another. At the Climax area, the species structure in both shallow and deep strata persisted throughout the study period. Within each stratum, differences in rank orders of species' abundances between station ALOHA and the Climax area are no greater than expected from physical mixing processes. However, abundances of species in the deeper recurrent groups were significantly lower at ALOHA.