STUDY OF THE DISTRIBUTION OF RECENT FORAMINIFERS FROM THE SOUTHWEST ATLANTIC OCEAN

CAROLINA MONTERO VÉNTOLA; BERNASCONI EMILIANA

Mar del Plata

Congreso; COLACMAR 2019; 2019

Universidad de Mar del Plata

In this work a preliminary analysis of the distribution and abundance of benthic foraminifera from a Argentinean shelf (39º 36´-40º 46´S to 56º 05´-60º 50´W) is presented. The purpose of this study is to increase the information about microorganisms along a transect between 50 to 280 m water depth and their environmental implications. For this, 10 samples of recent sediments were obtained on board the ship Puerto Deseado (MINDEF-CONICET) during an oceanographic campaign from 1st to 10th November, 2013, using a shipek surface-sediment sampler. All foraminiferal tests representing the total fauna (alive and dead) were extracted from 10 g of dry sediment analyzed by conventional methods (Boltovskoy, 1966). 26 species of foraminifera were distributed among a total abundance of 9788 individuals. The fauna was constituted by 99.9 % of calcareous specimens and 0.1 % agglutinated. The fauna along the transect was constituted by Trifarina angulosa (Williamson), Cibicides dispars (d´Orbigny), Uvigerina peregrina Cushman, and Globocassidulina subglobosa (Brady). Moreover, from statistical analysis three assemblages were recognized according to depth allowing to determine different environments. The first, at 50 m depth was characterized mainly by Buccella peruviana (d´Orbigny), Bulimina patagonica d´Orbigny, Pyrgo peruviana (d´Orbigny) and Elphidium gunteri Cole that reflect a shallow environment of inner shelf. The second (between 90 to 104 m depth) was represented mostly by Trifarina angulosa (Williamson) and Globocassidulina crassa (d´Orbigny) that suggested an influence of cold waters with high oxygen availability. Finally, the third assemblage (101 to 280 m depth) was constituted specially by Cibicides dispars (d´Orbigny), Epistominella exigua (Brady) and Cibicides aknerianus (d´Orbigny). This fauna reflected cold waters in both the open sea area between 100-200 m and batial area. In addition, the presence of species that adhere to the substrate suggests a high energy environment (Ishman and Martínez, 1995). Foraminifera fauna is characterized by species typically found in Malvinas current.