Interannual Variability in Seasonal Sea Surface Temperature and Chlorophyll a in Priority Marine Regions of the Northwest of Mexico

The northwest of Mexico has important zones for biodiversity conservation, denominated Priority Marine Regions (PMRs), and to study key oceanographic features related to ecological structure, it is necessary to understand environmental variability and observe climatic trends. Sea Surface Temperature (SST) is tightly associated with photosynthesis and serves as a control and driver for biological processes linked to the phytoplankton. Global climatic systems, like El Niño Southern Oscillation (ENSO), are responsible for the interannual and interdecadal variation in SST, since global circulation is modified by them. An important metric to assess phytoplanktonic biomass/photosynthesis is Chlorophyll a (Chl a), constituting the primary basis of the marine trophic web. The present study aims to examine the interannual oceanographic variability across 24 PMRs by employing monthly SST (°C) and Chl a (mg/m3) data derived from remote sensing instruments with spatial resolution of 4 km and 1 km from September 1997 to October 2018. We grouped the Priority Marine Regions into 18 main areas, based on a cluster analysis of Sea Surface Temperature. Significant differences were observed, showing higher SST levels during El Niño phase and higher Chl a concentration during La Niña phase, primarily in winter and spring, which will impact marine ecosystems.