Phytoplankton biomass and production off the Baja California Peninsula: 1997-2016

Abstract Between 1997 and 2016, the Investigaciones Mexicanas de la Corriente de California (IMECOCAL, Mexican Investigations of the California Current) program conducted measurements of chlorophyll a and phytoplankton production off Baja California. Here, we summarize the main results obtained during the survey period. Long-term means indicated that high productivity occurred along the coastal zone where upwelling occurs, and in a semi-permanent cyclonic gyre off Punta Eugenia. At the seasonal scale, the variability of integrated primary production showed differences with respect to integrated chlorophyll a variability. Integrated chlorophyll a exhibited maximum values during the coastal upwelling season in spring and summer, while minimum values occurred during the inflow of tropical-subtropical waters south of Punta Eugenia in autumn and winter. In contrast, the highest values of integrated primary production occurred in spring and summer to the north of Punta Eugenia, whereas to the south of this location, the highest values occurred in winter and autumn. This seasonal variability was associated with phytoplankton size and maximum photosynthetic rates. At the interannual scale, low productivity was associated with increased stratification during the subarctic water intrusion events and the “Blob” and El Niño events in 2015-2016. Productivity time-series were in agreement with the seasonal variability of the north Pacific Gyre Oscillation index. Given that phytoplankton is the first level of the marine food web, this study contributes to the understanding of regional variations in higher trophic levels at the seasonal and interannual scales.