PHYTOPLANKTON SPECIES STRUCTURE IN THE CENTRAL NORTH PACIFIC - IS THE EDGE LIKE THE CENTER

Phytoplankton samples were collected on July 14 and 18, 1985 from a station 460 km off the coast of northern Baja, California, near the eastern edge of the North Pacific central gyre. The vertical distributions and species structures at this edge station are compared with those observed over a 12 year period at a station 900 km north of Hawaii (central station). The edge station is somewhat colder and fresher than the central station but the chemical and general biological parameter are similar. At both locations, the phytoplankton are divided vertically into two assemblages, with a zone of transition near 100 m depth. Neither species composition nor dominance order within the shallow or deep zones at the edge station are significantly different from those at the central station. The spatial differences on a scale of 3200 km are the same as those observed at the central station over temporal intervals of 4-5 and 12 years, respectively, in the shallow and deep assemblages.