Surface copepod assemblages in shallow coastal waters off northeastern Yucatan Peninsula influenced by the Yucatan upwelling

Abstract

The seasonal variability of the Yucatan upwelling is known to exert a definite influence on environmental and biological conditions over the Yucatan Shelf. The present study is the first to analyze the variability of surface mesoplanktonic copepods in coastal waters off northeastern Yucatan Peninsula. Copepod samples and environmental parameters were obtained monthly in surface waters (∼1 m depth) at twelve sampling sites (<20 m depth). The sampling period included the upwelling season (April–September: Up) and representative months of non-upwelling (November–December: NUp). Differences in copepod assemblage attributes (abundance, species composition and diversity) and environmental parameters were analyzed among sampling sites, months, and seasons. Forty-two copepod species were recorded. Paracalanus quasimodo, a coastal euryhaline species, was widely dominant throughout the study period (relative abundance: 54%, frequency of occurrence: 94%). Univariate and multivariate statistical analyses indicated that copepod assemblages and environmental parameters remained spatially homogeneous but varied significantly over time. Two copepod assemblages were found concerning temporal changes in dominant species, its numerical and relative abundance, diversity and contrasting assemblage–environment​ relationships. The first assemblage occurred in the Up season, with a clear dominance of P. quasimodo (known as a coastal upwelling indicator species), high total copepod abundance, low diversity, and evenness, and positively influenced by high dissolved inorganic nutrients and chlorophyl-a concentrations. The second assemblage, present in the NUp season, also showed a dominance of P. quasimodo but with reduced relative abundance and increased of indicator species of oligotrophic waters, such as Clausocalanus furcatus and Farranula gracilis, low total copepod abundance, high diversity, and evenness, and positively influenced by salinity. The present results reinforce previous conclusions about the major influence that the Yucatan upwelling exerts on diverse marine biota off northeastern Yucatan Peninsula, improving the knowledge about the influence of local environmental parameters linked with upwelling variability to structuring the copepod assemblages.