A PHYSICAL ESTIMATE OF NEW PRODUCTION IN THE EQUATORIAL PACIFIC ALONG150-DEGREES-W

New production was estimated for the equatorial Pacific by quantifying the supply of nitrate into the euphotic zone. The turbulent flux of n itrate, estimated by assuming gradient transport and by direct measure ments of dissipation and nitrate concentration along a cross-equatoria l transect, was maximum (1-3 mmol m(-3) (d(-1)) at 0 degrees and 1 deg rees S. Poleward of the equatorial region, there was little vertical d iffusion of nitrate (<10(-3) mmol m(-2) d(-1)). An estimate was made o f the two-dimensional advective balance of nitrate between upwelling a nd the meridional divergence in the equatorial region. The net supply of nitrate into the euphotic zone (vertical supply minus meridional lo ss) was 4.3 mmol m(-2) d(-1) between 1 degrees N and 1 degrees S; betw een 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 incorpora tion of nitrate into particles but was comparable to the integrated lo cal rate of nitrate disappearance. The discrepancy between new product ion estimated from physical supply or from nitrate disappearance and t hat 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.