Copepod species assemblage and carbon biomass during two anomalous warm periods of distinct origin during 2014–2015 in the southern Gulf of California

Abstract Copepod species assemblage and biomass were studied during a weekly time series done during an anomalously warm and low sea surface Chlorophyll-a concentration period 2014–2015, compared with 2002–2018, at Cabo Pulmo National Park, Gulf of California, Mexico. Forty-nine copepod species accounted for 64% of the total zooplankton abundance. Three small copepods (Oncaea venusta 12.6%, Paracalanus parvus 11.5%, Clausocalanus jobei 8.6%) out of 45 species numerically dominated during 2014. The large copepods Subeucalanus subtenuis and Subeucalanus subcrassus out of 38 species recorded during 2015 increased in abundance accounting for 69% of copepod Carbon biomass. A Canonical Correspondence Analysis demonstrated SST drove copepod species assemblages. Copepod abundance was significantly higher during the cold (Nov–May) that during the warm (Jun–Oct) season and lower during Jan–Aug 2014 regional heatwave than during the Equatorial El Nino (Nov 2014–Dec 2015). Acartia tonsa was the only significant species indicator during the 2014 regional heatwave and Clausocalanus furcatus, Copilia mirabilis, and Cosmocalanus darwinii were significant species indicators of El Nino (2015). Copepod species assemblage had 87% tropical species during the Jan–Aug 2014 due to the regional heatwave that started the tropicalization of copepod community increasing to 95% of tropical species during El Nino 2015.