Nitrification and Nitrous Oxide Production in the Offshore Waters of the Eastern Tropical South Pacific
Bibliographic record
Abstract
Abstract Marine oxygen deficient zones are dynamic areas of microbial nitrogen cycling. Nitrification, the microbial oxidation of ammonia to nitrate, plays multiple roles in the biogeochemistry of these regions, including production of the greenhouse gas nitrous oxide (N 2 O). We present here the results of two oceanographic cruises investigating nitrification, nitrifying microorganisms, and N 2 O production and distribution from the offshore waters of the Eastern Tropical South Pacific. On each cruise, high‐resolution measurements of ammonium ([NH 4 + ]), nitrite ([NO 2 − ]), and N 2 O were combined with 15 N tracer‐based determination of ammonia oxidation, nitrite oxidation, nitrate reduction, and N 2 O production rates. Depth‐integrated inventories of NH 4 + and NO 2 − were positively correlated with one another and with depth‐integrated primary production. Depth‐integrated ammonia oxidation rates were correlated with sinking particulate organic nitrogen flux but not with primary production; ammonia oxidation rates were undetectable in trap‐collected sinking particulate material. Nitrite oxidation rates exceeded ammonia oxidation rates at most mesopelagic depths. We found positive correlations between archaeal amoA genes and ammonia oxidation rates and between Nitrospina ‐like 16S rRNA genes and nitrite oxidation rates. N 2 O concentrations in the upper oxycline reached values of >140 nM, even at the western extent of the cruise track, supporting air‐sea fluxes of up to 1.71 μmol m −2 day −1 . Our results suggest that a source of NO 2 − other than ammonia oxidation may fuel high rates of nitrite oxidation in the offshore Eastern Tropical South Pacific and that air‐sea fluxes of N 2 O from this region may be higher than previously estimated.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".