Hyperiid amphipod vertical distribution and community structure in the upper 100 m of the northwestern Caribbean Sea

The community structure and variability of the hyperiid amphipods of the Northwestern Tropical Atlantic (NWTA) remain largely unknown. We described and analyzed the hyperiid nictemeral, vertical, and horizontal distribution and the influence of environmental variables in the upper 100 m of the northwestern Caribbean Sea. We examined 196 zooplankton samples obtained during both day and nighttime at four depth strata from 49 sampling stations in January 2007. Up to 82 hyperiid species including 14 new regional records were identified and quantified. Both day/night and some interstrata differences were significant, particularly in reference to the uppermost and deepest strata. The local hyperiid community structure appeared to be profiled by the frequency and abundance variations of the two most abundant species, Lestrigonus bengalensis and Brachyscelus crusculum, both being most abundant in the uppermost (0–25 m) stratum. The horizontal distribution of the highest hyperiid abundance and diversity appears to be related to the influence of mesoscale processes like upwelling and cyclonic eddies. The Gulf of Honduras area had relatively low hyperiid abundances. The principal component analysis revealed density and temperature as the main factors explaining the local environmental variability. The canonical analysis of principal coordinates (CAP) showed that salinity and temperature strongly influenced the variability of the local hyperiid community. Overall, the two middle vertical strata (25–75 m) were relatively uniform; the main differences were found only between the uppermost and deepest strata. This study is the first to provide information regarding small-scale vertical distribution of hyperiid amphipods in the NWTA.