ABSTRACT: The islandmass of Trinidad perturbs the northwestward passage of the Guiana Current, inducing a wake and a stationary eddy off the northwest coast, in the North Coast Marine Area (NCMA). The oceanography is further complicated by the hypoycnal Orinoco Plume. Within the plume, Orinoco-derived outflow to the west and exiting Dragon’s Mouth abuts Amazon-derived water to the east along a front that trends NW from the island, east of the wake. Both the front and the eddy are reflected in 1958 maps of total (live + dead) foraminiferal fauna, Uvigerina parvula being more abundant (a) near the front, where convergent flow causes a high nutrient flux despite strong current action, and (b) below the eddy. The biofacies in nineteen seafloor sediment samples taken in 2010 north of the eddy but within the NCMA likewise show the front’s influence. A Cibicidoides norcomarensis n. sp. biofacies, recognized from cluster analysis, is developed to the west, beneath sluggishly flowing water within the wake. To the east and towards the front is developed a U. parvula biofacies. This reflects a higher nutrient flux along the front, despite its being within an area of stronger current action. Discriminant analysis distinguished these biofacies using only four species. Hoeglundina elegans provided the greatest negative separation and was more abundant in the C. nornocmarensis biofacies, while Eponides regularis, Pullenia subcarinata and Lenticulina submamilligera gave approximately equal positive separation. Diversity, measured using mean Shannon’s H, did not differ between the biofacies. There were, however, significant differences between the biofacies in mean dominance and in the mean of a benthic foraminiferal productivity index (BFPI), calculated from the sum of Bolivina + Bulimina +Uvigerina. The results presented here suggest that caution be taken when using Cibicidoides spp. and Uvigerina spp. to discern areas of higher current action and higher nutrient flux respectively at neritic depths in the vicinity of offshore fronts, as we found U. parvula within a higher flux but stronger current area than Cibicidoides norcomarensis.


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