SATELLITE-DERIVED ESTIMATES OF PHYTOPLANKTON BIOMASS OFF SOUTHERN BAJA-CALIFORNIA

All available estimates of photosynthetic pigment concentration derive d from data generated during 1978-1986 by the sensor Coastal Zone Colo r Scanner (CZCS) were used to interpret the spatial and temporal varia tions of phytoplankton biomass in a transept from Punta San Hipolito ( 27 degrees N, 114 degrees 30'W) to Cabo Corrientes (20 degrees 30'N, 1 05 degrees 30'W) off southern Baja California, Mexico. Highest pigment concentrations were present in areas near the coast. We suggest that they were due to upwelling and to interaction between the marine curre nts and local physiography. A recurrent front was observed off Cabo Sa n Lucas, with the strongest pigment concentration gradients at the end of spring and beginning of summer, during non-El Nino years. There wa s a clear seasonal variation near the coast. Immediately west of Baja California, high pigment values (3 to 8 mg m(-3)) were observed from F ebruary through August. Off Cabo Corrientes, high values occurred from January through May (5 to 8 mg m(-3)). These areas experience strong seasonal upwelling. EI Nino had a clear effect on pigment concentratio n, but it was not the only cause of interannual variation. There were relatively low pigment concentrations throughout the whole transept st arting in September 1982, with values often lower than 20% of those du ring the previous period. These low concentrations were maintained thr ough August 1984 at the entrance to the gulf, and through December 198 5 off the west coast of Baja California.