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Phytoplankton biomass and productivity off the Namibian Coast

AutorEstrada, Marta ; Marrasé, Cèlia
Fecha de publicación1987
EditorNational Inquiry Services Centre (South Africa)
CitaciónSouth African Journal of Marine Science 5(1): 347-356 (1987)
ResumenDuring September–October 1985 and April 1986, several transects of oceanographic stations were occupied off the coast of Namibia between 17°30′ and 26°30′S. During the 1985 cruise, active upwelling was apparent in all sections, but during 1986, upwelling was moderate. On both surveys, lowest inshore temperatures were found around 26°S. In spring 1985, chlorophyll-rich tongues were recorded off Lüderitz and Meob Bay and north of Walvis Bay, between 23 and 20°30′S. Concentrations of chlorophyll a were, in general, fairly homogeneous throughout a layer of 40–60 m depth, and correlation between surface chlorophyll a and integrated values for the water column was good. In April 1986, concentrations of chlorophyll a of 40 mg·m−3 were found off Walvis Bay; from there, bands of surface chlorophyll a concentrations exceeding 10 mg·m−3 extended towards the north and south-west. The vertical sections in April 1986 showed a certain degree of stratification, and in the northern one (at 17°30′S) there was a marked subsurface chlorophyll maximum offshore. Photosynthetically active irradiance and primary productivity (14C method) were measured at selected stations. The depth of the 1-per-cent light level ranged from 11 to 40 min 1985 and from 12 to 57 min 1986. Integrated primary production estimates at midday ranged from 0,04 to 0,10 g C·m−2·h−1 (down to the 3-per-cent light level) in spring 1985 and from 0,05 to 0,34 g C·m−2·h−1 (down to the 1,5-per-cent light level) in autumn 1986. The productivity indices (mg C·mg chlorophyll a −1·h−1) for comparable concentrations of chlorophyll a and the slope of the regression lines of integrated primary productivity on integrated or surface chlorophyll a were higher in autumn 1986 than in spring 1985
Descripción10 pages, 8 figures, 2 tables
Versión del editorhttps://doi.org/10.2989/025776187784522234
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