Living benthic foraminiferal species as indicators of cold-warm water masses interaction and upwelling areas

Abstract

The western South Atlantic continental margin, between 27° and 37°S, is dominated by four main water masses: cold-fresh Subantarctic Shelf Water (SASW), warm-salty Subtropical Shelf Water (STSW), cold upwelled South Atlantic Central Water (SACW), and fresh Plata Plume Water (PPW). Despite the large seasonal variability of PPW extension along the shelf, an intense and relatively stable temperature-salinity gradient separates the SASW and the STSW forming the Subtropical Shelf Front (STSF) around 32°S. The two dominant shelf water masses (SASW and STSW) arise from the process of mixing of oceanic waters. The SASW originates from the dilution of Subantarctic Water due to excess precipitation and continental runoff, and the STSW consists of modified warm tropical waters and South Atlantic Central Water (SACW) diluted below PPW. A previous article demonstrates distribution of Bulimina marginata, a shelf environment and deep-sea species of benthic foraminifera, is influenced by the front location and it can be used as a proxy of the STSF in sediment core analysis. Here we show three other infaunal living species inhabiting at the Continental margin: Buccella peruviana, Globocassidulina subglobosa and Uvigerina peregrina and their distribution limits show the interaction of Subantartic Shelf Water, Subtropical Shelf Water, and upwelling of SACW, in the bottom sediment of coastal studied areas.