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Seasonal cycle of N:P:TA stoichiometry as a modulator of CO 2 buffering in eastern boundary upwelling systems
Author(s) -
Gregor L.,
Monteiro P. M. S.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2013gl058036
Subject(s) - upwelling , alkalinity , redfield ratio , biogeochemical cycle , oceanography , anoxic waters , carbonate , environmental science , nitrate , ocean acidification , transect , denitrification , environmental chemistry , nutrient , geology , seawater , chemistry , nitrogen , phytoplankton , organic chemistry
In this study we use the southern Benguela upwelling system to investigate the role of nutrient and carbon stoichiometry on carbonate dynamics in eastern boundary upwelling systems. Six months in 2010 were sampled along a cross‐shelf transect. Data were classified into summer, autumn, and winter. Nitrate, phosphate, dissolved inorganic carbon, and total alkalinity ratios were used in a stoichiometric reconstruction model to determine the contribution of biogeochemical processes on a parcel of water as it upwelled. Deviations from the Redfield ratio were dominated by denitrification and sulfate reduction in the subsurface waters. The N:P ratio was lowest (7.2) during autumn once anoxic waters had formed. Total alkalinity (TA) generation by anaerobic remineralization decreased p CO 2 by 227 μatm. Ventilation during summer and winter resulted in elevated N:P ratios (12.3). We propose that anaerobic production of TA has an important regional effect in mitigating naturally high CO 2 and making upwelled waters less corrosive.