Chemical Oceanography of the Bransfield Strait: Micronutrient Compounds (SIBEX-Phase II Cruise. Chile)
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Date
1986
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Abstract
As a contribution to the international project Biological Investigations of Marine Antarctic Systems and Stocks (BIOMASS), the participating countries have been performing several biological - oceanographic cruises in the Bransfield Strait and adjacent areas. From January 24th to February 12th 1985, the Instituto Antártico Chileno (INACH) carried on a third biological- oceanographic cruise in the Bransfield area. This cruise was named SIBEX - Phase II (Second International BIOMASS Expedition Phase II). Such expedition was accomplished with the M/N Capitan Alcazar, performing 31 oceanographic stations in the Bransfield Strait, Gerlache Strait and Weddell Sea. The Escuela de Ciencias del Mar, Universidad Católica de Valparaíso, took part in this SIBEX-Phase II cruise, carrying out research on the chemical characteristics of the water masses present in that area. Water samples were collected, in the upper 700 meters, to analyze their micronutrient contents (phosphate, nitrate and silicate). A Nutrient- Autoanalizer System, built at the Universidad Católica de Valparaíso, was used to run the chemical analysis. The observed SIBEX- Phase II (austral summer 1985) cruise micronutrient contentc, was compared with micronutrient concentrations observed during (summer 1982) FIBEX cruise and (summer 1984) SIBEX- Phase I cruise, carried on by INACH. The larger 1985 smmer concentrations were statistically different (a= 0.05), to the ones observed in the same area, during 1981 summer and similar to the ones observed in the summer 1984. In this area, two water masses were detected: a) Bellingshausen Antarcctic Surface Water and b) Weddell Sea Surface Water. Beside theses water masses, four water bodies were also observed and they correspond to: a) Bransfield Strait Surface Water, b) Gerlache Strait Surface Water, c) Antarctic Peninsula Continental Shelf Surface Water and d) Bransfield Strait Deep Water. From the point of view of the micronutrient contents, the water masses are characterized by: a) Antarctic Surface Water: low silicate (<60 uM), compared to the Bransfield waters; Weddell Sea Surface Water: High phosphate, nitrate and silicate (> 1.8 uM, >18 uM and > 60 uM). In relation to the water bodies, they are characterized by: a) Bransfield Strait Surface Water: Hight phosphate, nitrate and silicate (> 1.8 uM, > 18 uM and > 70 uM); b) Gerlache Strait Surface Water: Low phosphate, nitrate and silicate (<1.0 uM, < 10 uM and < 70 uM); c) Antarctic Peninsula Continental Shelf Water: High phosphate, nitrate and silicate (> 2.0 uM, > 26 uM and > 80 uM); Bransfield Strait Deep Water: High phosphate, nitrate and silicate (>2.4 uM, >30 uM and > 90 uM). From the point of view of the T-S structures, six different T-S diagrams were identified. A zonation map was prepared to show where these structures were present. In relation to the temperature - micronutrient diagrams (T- Phosphate, T- Nitrate and T- Silicate), they were used as a complement to the T-S diagrams in the water masses structure characterization of the area.
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Micronutrientes, Oceanografía
Citation
Serie Científica, nº 35, pp. 7-37, 1986