Eufausidos epipelagicos de la Fosa de Cariaco

TitleEufausidos epipelagicos de la Fosa de Cariaco
Publication TypeJournal Article
Year of Publication2017
AuthorsGonzalez-Cebrero L, Varela R, Rojas-Marquez J
JournalMemoria de la Fundación La Salle de Ciencias Naturales
Volume74
Issue181-182
Start Page125
Pagination125-141
ISSN2443–4968
Abstract

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Composition, abundance, and horizontal distribution of euphausiids in the Cariaco Basin were determined from samples collected during two oceanographic campaigns: FOSA 1 in September 2008 (rainy season, non-upwelling period) and FOSA 2 in March 2009 (dry season, upwelling period). Upwelling was specifically manifested in the eastern coastal sector of the Basin. Samples were collected within the upper 200 m, or less in shallower stations, using oblique net tows and a mesh size of 200 μm. 14 euphausiids species of the genera Euphausia, Nematoscelis, Nictyphanes, Stylocheiron, and Tysanopoda were identified. During FOSA 1 these species were found in 13 stations; the most abundant species in this campaign were Euphausia tenera, E. gibboides and Stylocheiron carinatum. During FOSA 2, 11 species were identified in 11 stations with Euphausia mutica, E. gibboides, and E. tenera showing the highest abundances. Euphausia was the genus with more abundance during both campaigns: 61 % during the rainy, non-upwelling period, and 80 % during the dry, upwelling period. Stylocheiron represented 30 % of the euphausiid population during the upwelling period and dropped to 12 % during the non-upwelling period. The highest abundance (400–800 org/1000 m3) were observed during the upwelling period over the central and western sub-regions, where the basin is deepest (>200 m depth). Surprisingly, the highest euphausiids abundances were not observed in the eastern sub-region where upwelling is strongest. During the non-upwelling period, however, the maximum abundances were lower (300–500 org/1000 m3). During this period, the euphausid spatial distribution over the basin was more homogeneous and somewhat concentrated in the area where the basin is deepest. Species diversity was higher during the non-upwelling period (Shannon index=1.24–2.83) versus the upwelling period (0.42–2.51). Overall euphausiids abundances were not statistically different among FOSA 1 and FOSA 2 campaigns. We did find statically significant differences in the spatial distribution and species composition of the euphausiids populations between sampling periods. However, the species composition of the euphausiids population did vary between sampling periods; E. tenera and S. carinatum were dominant during the non-upwelling period whereas E. giboides y E. mutica dominated the population during the upwelling period.

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