Phytoplankton biomasses and hydrographic conditions during El Niño 1997-1998 in Bahia Concepcion, Gulf of California, Mexico

Abstract

The biomass of phytoplankton groups, particularly dinoflagellates as indicated by their signature pigment peridinin, and the physicochemical conditions in Bahía Concepción, Gulf of California are analyzed for the years 1997-1999, in order to observe the changes in phytoplankton and hydrographic structure linked to El Niño 1997-98. Three significant changes occurred in 1998 compared to 1997 and 1999: higher temperatures in the water column, lower nutrient and peridinin concentrations, and a 2 to 3 month delay of the stratification period. These data suggest the influence of Equatorial Surface Water (low nutrients, high temperatures) and a negative effect on the proliferation of dinoflagellate groups during El Niño 1997-98. Possible causes of the low dinoflagellate biomass are discussed.