Total dissolved nitrogen and phosphorus concentrations at US-JGOFS Station ALOHA: Redfield reconciliation

David M. Karl, Georgia Tien, John Dore and Christopher D. Winn

Abstract

Twenty-two water column profiles (0-4500 m) of total dissolved nitrogen (TDN) and phosphorus (TDP) concentrations have been collected over a 2-year period at the US-JGOFS time-series Station ALOHA. These data indicate that the N: P molar ratio (mean, 16.74; standard deviation, 2.95; n = 417) in the central Pacific Ocean is not significantly different from that predicted a priori based upon current models of the bioelemental composition of plankton. An examination of the literature and new data from our laboratory using direct high-temperature combustion methods for both TDP and TDN support the validity of historical oceanic analyses. Despite the substantially higher DOC values in oligotrophic Pacific Ocean surface waters, TDN (and consequently dissolved organic nitrogen [DON]) and TDP (and consequently dissolved organic phosphorus [DOP]) do not appear to have been underestimated.