Seasonal variability of chlorophyll a and their response to El Nino and La Nina conditions in the Northern Gulf of California

摘要

In order to determinate the seasonal variability concentrations of chlorophyll-a (Clo-a) derived from satellite observations, and their responses to El Nino and La Nina conditions in the northern Gulf of California (NGC), we used monthly sea color composites from January 1997 to December 2011 from the OCTS and SeaWiFS sensor. The Clo-a seasonality indicate in winter-spring maxima and summer-autumn minimum, with a predominance of the annual signal During El Nino 1997-1998 Clo-a showed low concentrations. During El Nino 2002-2003 the Clo-a show low influence. In La Nina 2007 Clo-a response was positive with high values. In 2011 where registered the highest Clo-a concentration of the entire study period, as result of La Nina phase. From 2003 to 2007 conditions were considered 'normal' in the system. The average pattern of time series suggests that NGC is eutrophic and the interannual variability of Chl-a is influenced by adjacent Pacific Ocean forcing, suggested by a significant inverse relationship of Chl-a and the Multivariate ENOA index (MEI; ENOA: El Nino Austral Oscillation). We propose that shifts from a strong El Nino (1997-1998) to La Nina conditions (1999), the phytoplankton biomass response was low because a great oceanography conditions changes (wind, stability, etc.), however with the shifts from El Nino weak (2009-2010) to La Nina (2011), these conditions represent less stress with a suitable phytoplankton response and the biomass increases.