A monthly survey of the partial pressure of CO 2 (pCO 2 ) was carried in the Southern Bight of the North Sea (SBNS) from June 2003 to May 2004. The spatial variability of the surface distribution of the pCO 2 was relatively small (within a range of 10-70 ΞΌatm) compared to the amplitude in the seasonal signal (βΌ 260 ΞΌatm). On an annual scale, the pCO 2 dynamics appeared to be controlled by biological processes (primary production in springtime and respiratory processes in summer), rather than temperature (in summer). The comparison with measurements carried out in 2001 and 2002 (13 cruises) shows that the inter-annual variability of pCO 2 was close to the range of the spatial variability and mostly observed in spring, associated to biological processes (primary production). Net ecosystem production estimated from dissolved inorganic carbon (DIC) temporal variations showed that the SBNS is autotrophic, at an annual rate of 6.3 mol C m -2 yr -1 . The decoupling in time between autotrophy in spring and heterotrophy in summer, associated to the relatively rapid flushing time of the water mass in the area (βΌ 70 days), might allow the export of a fraction of the springtime synthesized organic matter to the adjacent areas of the North Sea. The SBNS was on a yearly basis a sink of atmospheric CO 2 at a rate of -0.7 mol C m -2 yr -1 .