Distribution of pteropods (Mollusca: Gastropoda: Thecosomata) in surface waters (0-100 m) of the Western Caribbean Sea (winter, 2007)

Abstract

The main goal of this survey was to study the vertical and horizontal distribution of the thecosome pteropods in the upper 100 m of the western Caribbean Sea. Zooplankton was collected at 60 stations in January 2007 at stratified depth intervals of 25 m from the surface to 100 m. The community was analyzed for diversity, evenness, species richness, and similarity. We recorded 36 taxa 12 of which are new records for the western Caribbean. The most abundant taxa were Limacina inflata, L. trochiformis, Creseis acicula f. clava, Cuvierina columnella atlantica, and Hyalocylis striata. In general, these taxa showed a similar pattern, their highest abundances occurred consistently in 0-25 m layer in both night and day samples; abundance decreased with depth. Significant day/night differences were found in the composition and abundance of pteropods, differences among depth intervals were non-significant. Our results showed that the upper 25 m harbored the highest species richness, diversity, and vertical abundance of pteropods, thus providing unprecedented detail with respect to previous surveys. The local community structure of the pteropods is determined largely by vertical day/night migrations. Pteropods tended to be most abundant in the southern and northern sectors of the area, but highest diversity and species richness were recorded in the central sector. Overall, the low variability of the hydrographic conditions and the mixed horizontal distribution of the clusters from the similarity analysis suggest that day/night migratory patterns of the most abundant taxa are determinant of the observed variability of the pteropod community.