Temporal changes in the epipelagic copepod assemblage at Gorgona Island, Colombian Eastern Tropical Pacific ocean

Abstract

Temporal variations in the hydrographic conditions of the Eastern Tropical Pacific (ETP) can modulate the assemblage structure of marine organisms, including copepods. While this taxonomic group has been widely recognized as important in the energy flow of the pelagic environment, fundamental ecological aspects are still unknown particularly possible relationships with oceanographic variations that have been described for ETP. In this paper, we evaluated the intra-annual and interannual variation of structure, richness, diversity, and similarity of the epipelagic copepod assemblage of Gorgona Island (Colombian ETP) based on samples collected during six oceanographic campaigns carried out between 2010 and 2016. We found significant changes in the oceanographic conditions and abundance of copepods between periods and years. Seven significant clusters were identified: five for each sampled period and two for the period of October 2010. Ditrichocorycaeus andrewsi, Oncaea clevei, Paracalanus parvus, and Subeucalanus pileatus were the species with the greatest contribution to group formation. Our results suggest that the intra-annual changes in the assemblage of epipelagic copepods recorded in Gorgona Island are a consequence of the displacement of the Intertropical Convergence Zone throughout the ETP during the year. This is due to the fact that during the periods of March they respond to the entry of subsurface waters from the Ensenada de Panama, and during the periods of October respond to the increase of the continental runoff on the pelagic environment of Colombian ETP.