A PHYSICAL ESTIMATE OF NEW PRODUCTION IN THE EQUATORIAL PACIFIC ALONG 150-DEGREES-W

New production was estimated for the equatorial Pacific by quantifying the supply of nitrate into the euphotic zone. The turbulent flux of nitrate, estimated by assuming gradient transport and by direct measurements of dissipation and nitrate concentration along a cross-equatorial transect, was maximum (1-3 mmol m(-3) (d(-1)) at 0 degrees and 1 degrees S. Poleward of the equatorial region, there was little vertical diffusion of nitrate (<10(-3) mmol m(-2) d(-1)). An estimate was made of the two-dimensional advective balance of nitrate between upwelling and the meridional divergence in the equatorial region. The net supply of nitrate into the euphotic zone (vertical supply minus meridional loss) was 4.3 mmol m(-2) d(-1) between 1 degrees N and 1 degrees S; between 5 degrees N and 5 degrees S, it was 1.9 mmol m(-2) d(-1) The total supply of nitrate was larger than the concurrently measured incorporation of nitrate into particles but was comparable to the integrated local rate of nitrate disappearance. The discrepancy between new production estimated from physical supply or from nitrate disappearance and that estimated from nitrate incorporation into particles suggests that uptake by small cells (< 1 mu m), dissolved organic N, or both play an important role in the equatorial region.