Phytoplankton species structure in the central North Pacific: Is the edge like the center?

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