Tintinnid distributions in the Strait of Magellan (Chile)

Abstract In the Strait of Magellan and in the adjacent Pacific and Atlantic Ocean shelf tintinnids were studied during three oceanographic cruises (November 1989, March–April 1991, and April 1995). Total tintinnid abundances were higher in the first cruise and dramatically decreased in the other two late summer cruises. As a general rule, abundances were higher at the surface and in the Atlantic sector. A total of 47 tintinnid species were found. There was not a single species, which could be identified as indicator of a specific water mass. For each cruise, cluster analysis applied on a species/samples matrix identified station sets characterized by a specific tintinnid association. Angosturas entrance was characterized by agglutinated lorica tintinnids, typical of the Atlantic waters, while the Pacific sector by hyaline species. In Punta Arenas basin, a peculiar tintinnid community was clearly identified, although water masses derived from the mixing process between the Pacific and Atlantic waters. Overall, tintinnid communities maintained the structure typical of the water mass despite advection and/or mixing. The main result of this study was to demonstrate that the structure of the tintinnid species association could be used as indicator of the origin of water masses.