Benthic foraminiferal biogeography in the southeast Caribbean Sea

Abstract

The SE Caribbean Sea is not ubiquitously oligotrophic. It is subject to the Caribbean Current, which is an extension of the Guiana Current and flows NW across the sea. It is also impacted by outflow from the Orinoco River, which produces a hypopycnal plume that is transported across the sea by the Caribbean Current, and by local upwelling, which occurs at distinct focuses. This paper uses non-metric multidimensional scaling (NMDS) to examine the impact of this oceanographic complexity on the distributions, based on species presence/absence, of neritic to upper bathyal benthic foraminifera. Sites within the ambit of the Orinoco Plume (Orinoco offshore, Trinidad East Coast Marine Area [ECMA], Trinidad North Coast Marine Area [NCMA), offshore NW Tobago, Bequia) are closely grouped by NMDS, despite the NCMA being subject to minor upwelling and Bequia only seasonally laying within the plume. The Paria and Araya Peninsula areas, though geographically close and both subject to upwelling, do not cluster closely. This indicates that the two upwelling focuses induced some biogeographic separation. The Isla La Tortuga, being bathed with oligotrophic water, plotted far from the eutrophic Orinoco Plume sites. The upwelling Paria Peninsula site, adjacent to the Orinoco Plume, yielded seventeen species of Bolivina (the greatest species richness for this genus of any of our sites), whereas Isla La Tortuga yielded only four. The Trinidad NCMA, likewise a site of upwelling, presented the second highest number of species of Bolivina, yielding twelve. That the Plataforma Deltana site plotted far from all others reflects its bathyal position beyond the Orinoco Plume.