A dual 13C/15N isotopic technique was used to estimate carbon and nitrogen uptake rates during the 1-year-long Programme Oc¿an Multidisciplinaire M¿so Echelle (POMME) experiment in the northeast basin of the Atlantic Ocean (16¿--22¿W, 38¿--45¿N). Rates of primary production ranged from 2.26 ¿moles L-1 d-1 in winter to maximum surface values of 7.8 ¿moles L-1 d-1 during the spring season. Nitrate assimilation was intense since the beginning of winter and accounted for 3--7 mmoles m-2 d-1 in the first 80 m depth of the water column. Rates increased to 5--9 mmoles m-2 d-1 during the spring season. NO3- uptake rates during the late summer season were close to winter values. Ammonium assimilation activity balanced the uptake of nitrate for all seasons. The seasonal f ratio was close to 0.28 in winter, increased to 0.34 in spring, and, finally, decreased to 0.25 in late summer. Annual carbon uptake rates for the entire POMME area accounted for 16.9 moles C m-2 yr-1. From this result, annual new production could be estimated to 5.7 moles C m-2 yr-1.