Other
Scientific paper
Feb 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006e%26psl.242..186p&link_type=abstract
Earth and Planetary Science Letters, Volume 242, Issue 1-2, p. 186-204.
Other
6
Scientific paper
This article presents data on the isotopic composition of pore water ammonium and Norg in the anoxic sediments of the Santa Barbara Basin and the Eastern Subtropical North Pacific (ESNP) region. Ammonium δ15N behaves differently in the two regions, reflecting variability in bacterial processes of sedimentary nitrogen cycling. In Santa Barbara Basin, stoichiometry of TCO2 and NH4+ production defined by pore water chemistry indicates that the only reaction influencing pore water ammonium concentration in these sediments appears to be organic matter decomposition. Pore water ammonium was found to be 1 3‰ heavier than decomposing organic matter. In contrast, the upper 15 30 cm of ESNP pore waters have ammonium with δ15N that is more than 10‰ heavier than decomposing organic matter. At greater depth, the δ15N of deeper pore waters approaches that of decomposing organic matter. Mass balance calculations indicate that the observed isotopic enrichment is not due to the preferential loss of isotopically enriched organic matter. Pore water profiles show that the zone with heavy isotopes is characterized by a TCO2/NH4+ inputs ratio of 4 or less. We attribute this to the presence of Thioploca bacteria, who transport NO3- to depth and reduce it to NH4+ while oxidizing sulfide. Based on pore water stoichiometry, and reaction diffusion modeling of pore water isotopic composition we propose that the 15N-enriched ammonium is produced as the result of chemosymbiosis between Thioploca and Anammox-like bacteria in these sediments. Our work provides the new insights into benthic microbial ecology, and the role of coupled individual metabolic pathways in sedimentary nitrogen cycling. In Santa Barbara Basin, factors which contribute to the isotopic fractionation of 1 3‰ between pore water ammonium and solid Norg were also considered. In this sediments, ˜23% of the rain of organic nitrogen is lost to diagenesis, therefore, the isotopic effect of degradation on the residual Norg is estimated to be small, - 0.7‰. The most likely cause of fractionation is preferential degradation of an isotopically heavier, more labile marine fraction relative to an isotopically lighter, more refractory terrestrial component of the organic matter, but other possibilities cannot be ruled out. When corrected for the observed fractionation, it appears that the δ15N of these sediments may represent non-steady state conditions.
Berelson William M.
Bernhard Joan M.
Douglas Robert
Hammond Douglas E.
Prokopenko Maria G.
No associations
LandOfFree
Nitrogen cycling in the sediments of Santa Barbara basin and Eastern Subtropical North Pacific: Nitrogen isotopes, diagenesis and possible chemosymbiosis between two lithotrophs (Thioploca and Anammox)—“riding on a glider” does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Nitrogen cycling in the sediments of Santa Barbara basin and Eastern Subtropical North Pacific: Nitrogen isotopes, diagenesis and possible chemosymbiosis between two lithotrophs (Thioploca and Anammox)—“riding on a glider”, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nitrogen cycling in the sediments of Santa Barbara basin and Eastern Subtropical North Pacific: Nitrogen isotopes, diagenesis and possible chemosymbiosis between two lithotrophs (Thioploca and Anammox)—“riding on a glider” will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1489048