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An Appraisal of the Stoichiometry of Dissolved Oxygen/Nutrient Inter-Relationships in the Upwelling System Off Northern Chile

Published online by Cambridge University Press:  11 May 2009

Anthony G. Davies  and
Carmen E. Morales
Anthony G. Davies*
Affiliation:
Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, PL1 2PB.
*
†Estacion de Biología Marina, Departmento de Oceanografía, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Conceptión, Casilla 44, Dichato, VIII Región, Chile
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Extract

Using vertical profile data from the upwelling system off northern Chile, the slopes of dissolved oxygen/nutrient concentration regressions have been analysed, in conjunction with a value of 1·4 for the molar ratio of net community oxygen production to nitrate-driven carbon dioxide assimilation, to investigate the stoichiometric inter-relationships between photosynthetic oxygen production and carbon dioxide and nutrient consumption. There was little interseasonal variation in ΔCO2/ΔDIN (nitrate+nitrite) molar ratios, ranging from 10·3 to 11·6 in the near-shore zone of active upwelling and 6·7 to 9·0 in mid-water, between 25 and 50 m depth offshore. Although the former range exceeded the value expected from Redfield-Richards stoichiometry (6·6) by more than 50%, it was in line with published ratios for phytoplankton blooms in coastal and oceanic waters. Mean ΔDIN/ΔPO4 ratios were similar for the near-shore stations and the mid-water, ranging respectively from 7·0 to 10·7 and 8·4 to 11·5, these subRedfield-Richards values mirroring the ratios of the nutrient concentrations in the water and probably implying ‘luxury’ consumption of phosphate. Seasonal variations in the ΔO2/ΔPO4 ratios for the near-shore zone are shown to be consistent with the view that, in the austral spring and summer when upwelling is strongest in the area, the main source of the water coming to the surface is the Peru-Chile Undercurrent, whereas in the autumn, it could be of subantarctic origin.

Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 78 , Issue 3 , August 1998 , pp. 697 - 706
Copyright
Copyright © Marine Biological Association of the United Kingdom 1998

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