Satellite-derived estimates of phytoplankton biomass off Southern Baja California

Abstract

All available estimates of photosynthetic pigment concentration derived from data generated during I978-1986 by the sensor Coastal Zone Color Scanner (CZCS) were used to interpret the spatial and temporal variations of phytoplankton biomass in a transept from Punta San Hipólito (27ºN, 114º30’W) to Cabo Corrientes (20º30’N. 105º30’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 currents and local physiography. A recurrent front was observed off Cabo San Lucas. with the strongest pigment concentration gradients at the end of spring and beginning of summer, during non-El Niño years. There was a clear seasonal variation near the coast. immediately west of Baja California. high pigment values (3 to 8 mg m^–3) were observed from February through August. Off Cabo Corrientes, high values occurred from January through May (5 to 8 mg m^–3). These areas experience strong seasonal upwelling. El Niño had a clear effect on pigment concentration, hut it was not the only cause of interannual variation. There were relatively low pigment concentrations throughout the whole transept starting in September 1982, with values often lower than 20% of those during the previous period. These low concentrations were maintained through August 1984 at the entrance to the gulf, and through December 1985 off the west coast of Baja California.