Journal
ENVIRONMENTAL MICROBIOLOGY
Volume 19, Issue 12, Pages 4838-4850Publisher
WILEY
DOI: 10.1111/1462-2920.13457
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Funding
- NSF [ANT 08-23101, OCE 11-53930, OCE 12-34388]
- U.S. National Science Foundation [ANT 08-38996, OCE 06-20959, OCE 10-29742, OCE 11-29260]
- Directorate For Geosciences
- Division Of Ocean Sciences [1237140, 1335838] Funding Source: National Science Foundation
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Urea nitrogen has been proposed to contribute significantly to nitrification by marine thaumarchaeotes. These inferences are based on distributions of thaumarchaeote urease genes rather than activity measurements. We found that ammonia oxidation rates were always higher than oxidation rates of urea-derived N in samples from coastal Georgia, USA (means +/- SEM: 382 +/- 35 versus 73 +/- 24 nmolL(-1)d(-1), Mann-Whitney U-test p<0.0001), and the South Atlantic Bight (20 +/- 8.8 versus 2.2 +/- 1.7 nmolL(-1)d(-1), p=0.026) but not the Gulf of Alaska (8.8 +/- 4.0 versus 1.5 +/- 0.6, p>0.05). Urea-derived N was relatively more important in samples from Antarctic continental shelf waters, though the difference was not statistically significant (19.4 +/- 4.8 versus 12.0 +/- 2.7 nmolL(-1)d(-1), p>0.05). We found only weak correlations between oxidation rates of urea-derived N and the abundance or transcription of putative Thaumarchaeota ureC genes. Dependence on urea-derived N does not appear to be directly related to pH or ammonium concentrations. Competition experiments and release of (NH3)-N-15 suggest that urea is hydrolyzed to ammonia intracellularly, then a portion is lost to the dissolved pool. The contribution of urea-derived N to nitrification appears to be minor in temperate coastal waters, but may represent a significant portion of the nitrification flux in Antarctic coastal waters.
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