Phytoplankton in the surface and chlorophyll maximum off southern California in August, 1978

Abstract

A synoptic sampling of 30 stations in a 25 km ×40 km grid close to the southern California coast revealed that chlorophyll and phytoplankton biomass were higher nearshore and to the south, where relatively large dinoflagellates dominated. A subsurface chlorophyll maximum was present at each station, near the nitracline and 10% light level. Nearshore and to the south, these maxima represented higher levels of phytoplankton biomass than at the surface whereas at the other stations, chlorophyll maxima could be attributed to physiological changes in chlorophyll content of small flagellated phytoplankton rather than to the accumulation of phytoplankton at depth. Univariate and multivariate statistical procedures were used to demonstrate that phytoplankton assemblages separated by tens of meters in the vertical were just as different as those separated by tens of kilometers in the horizontal. We conclude that residence time of water near the coast is of great importance to the determination of the abundance and taxonomic characteristics of phytoplankton, and that advection of offshore water towards the coast was the major determinant of the pattern observed during our study.