Planktonic Foraminifera from south-western Atlantic epipelagic waters: Abundance, distribution and year-to-year variations

• Main Author: Boltovskoy, Demetrio
• Language: unknown
• Published: 2000
• Subjects: Atlantic Ocean; brazil; chlorophyll a; geographic distribution; marine environment; paleoecology; population abundance; species difference; tropics; zooplankton; abundance; annual variation; foraminifera; spatial distribution; Globigerina bulloides; Globigerina quinqueloba; Globigerinita uvula; Globigerinoides ruber; Globigerinoides trilobus; Neogloboquadrina pachyderma; Antarctic; Argentina; Antarc*; Planktonic foraminifera
• Online Access: https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00253154_v80_n2_p203_Boltovskoy; https://hdl.handle.net/20.500.12110/paper_00253154_v80_n2_p203_Boltovskoy

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 south-western 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 six 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, G. 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 regimes 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, G. 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. Fil:Boltovskoy, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.