Pelagic ecosystem response to interannual variability off Baja California

Abstract

Seasonal anomalies of salinity, phytoplankton chlorophyll a, and zooplankton volume off Baja California were examined from data obtained during 2001-2007. The analyses helped to identify a strong effect of physical processes on the pelagic ecosystem, diminishing near surface salinity and water column integrated phytoplankton biomass, and enhancing zooplankton volume. These changes are associated with an increase of the Pacific Decadal Oscillation (PDO) index, characterizing a warm phase of the index from summer 2002 to at least summer 2006. Negative chlorophyll a anomalies appear to respond to zooplankton grazing activity, with a possible "top down" effect during this period. Empirical orthogonal functions (EOFs) of Ekman drift reveal the seasonal and interannual patterns that describe the influence of upwelling zones, and there was a strong response to changes in the equatorward wind forcing from 2002 to 2006. The relationship between negative salinity anomalies and the two temporal EOF modes of Ekman drift was evident as a result of relaxation of coastal upwelling during this period. After 2006, the PDO index showed more neutral or negative values, defining the beginning of a cool phase, with positive nearsurface salinity anomalies off Baja California.

Effects of the interannual variability of water column stratification on phytoplankton production and biomass in the northern zone off Baja California

“…The monthly composite images (spatial resolution of 4 × 4 km) of SST and CHL concentrations derived from the MODIS-Aqua P m B (Lavaniegos et al 2002). A partir de 2002 y hasta 2006, el debilitamiento del giro de Alaska causó la intrusión anómala de agua subártica en el océano frente a la península de Baja California (Durazo 2009), generando disminución en la producción y biomasa del fitoplancton (Gaxiola-Castro et al 2008, Espinosa-Carreón et al 2015. Recientemente se registró que durante el calentamiento del océano generado por el evento de "The Warm Blob" durante 2013 y 2014 y por El Niño 2015-2016 se produjo la reducción más alta de biomasa y producción del fitoplancton de los últimos 13 años en el límite sur de la corriente de California (Gómez-Ocampo et al 2017).…”

“…Desde 1997, el programa Investigaciones Mexicanas de la Corriente de California (IMECOCAL) ha realizado el monitoreo del océano frente a las costas de la península de Baja California. Esto ha permitido conocer y entender diversos procesos físicos, biológicos y químicos que ocurren en dicha región (Durazo y Baumgartner 2002, Lavaniegos et al 2002, 2015Espinosa-Carreon et al 2004, Gaxiola-Castro et al 2008, Jeronimo y Gomez-Valdes 2010, Durazo 2015, Espinosa-Carreón et al 2015, Martinez-Fuentes et al 2016, Gómez-Ocampo et al 2017, Lavaniegos 2017. Sin embargo, aunque se tiene información de variables físicas, biológicas y químicas, aún falta entender cómo los procesos físicos influyen sobre los cambios interanuales de la biomasa y producción del fitoplancton en la columna de agua.…”

“…During La Niña 1998-1999, intensification of coastal upwelling events led to increased phytoplankton biomass (Lavaniegos et al 2002). From 2002 to 2006, the weakening of the Alaska Gyre caused the anomalous intrusion of subarctic water off Baja California (Durazo 2009), leading to a decrease in phytoplankton production and biomass (Gaxiola-Castro et al 2008, Espinosa-Carreón et al 2015. The ocean warming caused by "The warm Blob" during 2013 and 2014 and El Niño 2015-2016 produced the highest reduction of…”

“…Since 1997, the Investigaciones Mexicanas de la Corriente de California (Mexican Investigations on the California Current; IMECOCAL for its acronym in Spanish) program has surveyed the region off Baja California. This has allowed for better knowledge and understanding of the many oceanic physical, biological, and chemical processes in this region (Durazo and Baumgartner 2002, Lavaniegos et al 2002, 2015Espinosa-Carreon et al 2004, Gaxiola-Castro et al 2008, Jeronimo and Gomez-Valdes 2010, Durazo 2015, Espinosa-Carreón et al 2015, Martinez-Fuentes et al 2016, Gómez-Ocampo et al 2017, Lavaniegos 2017. However, although there is available information on physical, biological, and chemical variables, there is still insufficient understanding on how physical processes influence the interannual changes in phytoplankton biomass and production in the water column.…”

Response of primary producers to the hydrographic variability in the southern region of the California Current System

“…The response of primary producers to changes in oceanographic conditions, in terms of biomass, which is estimated using the concentration of chlorophyll (Chla), off the coast of Baja California has been documented based on both measurement data (Gaxiola-Castro et al 2008 and remote sensing data (Espinosa-Carreón et al 2004). On a seasonal scale, the southern portion of the CCS typically shows high Chla concentrations during spring due to the intensification of coastal upwelling, but these concentrations decrease during summer due to the combined effect of the weakening of upwelling favorable winds and the increase in water stratification.…”