Short-term variability of fCO2 in seawater and air-sea CO2 fluxes in a coastal upwelling system (Ria de Vigo, NW Spain)

Coastal upwelling systems are regions with highly variable physical processes and very high rates of primary production and very little is known about the effect of these factors on the short-term variations of CO(2) fugacity in seawater (fCO(2)(w)). This paper presents the effect of short-term variability (< 1 week) of upwelling-downwelling events on CO(2) fagacity in seawater (fCO(2)(w)), oxygen, temperature and salinity fields in the Ria de Vigo (a coastal upwelling ecosystem). The magnitude of fCO(2)(w) values is physically and biologically modulated and ranges from 285 muatm in July to 615 muatm in October. There is a sharp gradient in fCO(2)(w) between the inner and the outer zone of the Ria during almost all the sampling dates, with a landward increase in fCO(2)(w). CO(2) fluxes calculated from local wind speed and air-sea fCO(2) differences indicate that the inner zone is a sink for atmospheric CO(2) in December only (-0.30 mmol m(-2) day(-1)). The middle zone absorbs CO(2) in December and July (-0.05 and -0.27 mmol(.)m(-2) day(-1), respectively). The oceanic zone only emits CO(2) in October (0.36 mmol(.)m(-2) day(-1)) and absorbs at the highest rate in December (-1.53 mmol(.)m(-2) day(-1)). (C) 2002 Elsevier Science B.V All rights reserved.