Basin-scale distribution of NH 4 + and NO 2 − in the Pacific Ocean

We used more than 25,000 nutrient samples to elucidate for the first time basin-scale distributions and seasonal changes of surface ammonium (NH 4 + ) and nitrite (NO 2 − ) concentrations in the Pacific Ocean. The highest NH 4 + , NO 2 − , and nitrate (NO 3 − ) concentrations were observed north of 40°N, in the coastal upwelling region off the coast of Mexico, and in the Tasman Sea. NH 4 + concentrations were elevated during May–October in the western subarctic North Pacific, May–December in the eastern subarctic North Pacific, and June–September in the subtropical South Pacific. NO 2 − concentrations were highest in winter in both hemispheres. The seasonal cycle of NH 4 + was synchronous with NO 2 − , NO 3 − , and satellite chlorophyll a concentrations in the western subtropical South Pacific, whereas it was synchronous with chlorophyll- a but out of phase with NO 2 − and NO 3 − in the subarctic regions.