Bibliography - R. Ho

1. Sigman, Daniel, J. Granger, P. J. DiFiore, K. K. Lehman, R. Ho, G. Cane, and A. van Geen, 2005: Coupled nitrogen and oxygen isotope measurements of nitrate along the eastern North Pacific margin. Global Biogeochemical Cycles, 19(GB4022), doi:10.1029/2005GB002458
   [ Abstract ]

   Water column depth profiles along the North Pacific margin from Point Conception to the tip of Baja California indicate elevation of nitrate (NO₃) ¹⁵N/¹⁴N and ¹⁸O/¹⁶O associated with denitrification in the oxygen-deficient thermocline waters of the eastern tropical North Pacific. The increase in δ¹⁸O is up to 3% greater than in δ¹⁵N, whereas our experiments with denitrifier cultures in seawater medium indicate a 1:1 increase in NO₃ δ¹⁸O and δ¹⁵N during NO₃ consumption. Moreover, the maximum in NO₃ δ¹⁸O is somewhat shallower than the maximum in NO₃ δ¹⁵N. These two observations can be summarized as an ‘‘anomaly’’ from the 1:1 δ¹⁸O-to-δ¹⁵N relationship expected from culture results. Comparison among stations and with other data indicates that this anomaly is generated locally. The anomaly has two plausible interpretations: (1) the addition of low-δ¹⁵N NO₃ to the shallow thermocline by the remineralization of newly fixed nitrogen, or (2) active cycling between NO₃ and NO₂ (coupled NO₃ reduction and NO₂ oxidation) in the suboxic zone.

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