Planktonic Foraminifera from southwestern Atlantic epipelagic waters: abundance, distribution and year-to-year variations

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Authors: Boltovskoy, Esteban, Boltovskoy, Demetrio, Brandini, Frederico
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2000
• Subjects: Antarc*; Antarctic; Neogloboquadrina pachyderma; Planktonic foraminifera
• Online Access: http://dx.doi.org/10.1017/s0025315499001794; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315499001794

The abundance and latitudinal and vertical (0-100 m) distribution of planktonic Foraminifera was investigated on the basis of 38 samples collected in November 1994 in the southwestern Atlantic Ocean (34-60°S, along 51-56°W). Mean foraminiferal densities were 1.5 ind. l −1 (range: 0.15.9 ind. l −1 ), with highest concentrations in subsurface waters (20-50 m). Couplings between the distribution of chlorophyll a and foraminiferal abundances were very loose. Distribution patterns of the 15 species recorded allowed 6 distinct areas to be defined along the transect surveyed. From north to south these are: Subtropical (dominated by Globigerinoides ruber and G. trilobus ), Cold intrusion ( Globigerinita uvula ), Transitional-Subtropical and Transitional ( Globigerina bulloides , Globigerina quinqueloba ), Subantarctic ( G. quinqueloba ), and Antarctic ( Neogloboquadrina pachyderma , left coiling). Close comparisons with the yields of a similar data set collected in November 1993 show very good agreement. Foraminiferal thermic régimes were also similar in 1993 and in 1994, but for some species significant differences with previous data were detected. While the southwards extensions of the ranges of warm water species are fairly well circumscribed by the Brazil current-influenced waters, several foraminifers widely used as indicators and palaeoindicators of cool waters (in particular Globigerina bulloides , Globigerina quinqueloba and Globigerinita uvula ) were recorded in very significant numbers at temperatures as high as 20-24°C. The implication of these findings for hydrological, ecological, and palaeoecological interpretations is discussed.