Nitrogen uptake by heterotrophic bacteria and phytoplankton in Arctic surface waters
Bibliographic record
Abstract
We estimated rates of heterotrophic bacterial and phytoplankton uptake of nitrate, ammonium, and urea using 15N-labelled nitrogen and specific metabolic inhibitors of prokaryote and eukaryote nitrogen metabolism in the surface waters of the North Water (northern Baffin Bay) during autumn that were characterized by the absence of cyanobacteria (comprising prochlorophytes). The percentage of nitrate + ammonium uptake by heterotrophic bacteria ranged between 44 and 78% of the measured total uptake and was the highest when the phytoplankton biomass was relatively low (<2 μg Chlorophyll a L−1). Phytoplankton accounted for a larger fraction (e.g., 58–95%) of urea uptake than heterotrophic bacteria. When our results are combined with those from previous studies carried out in diverse temperate and polar areas, it appears that heterotrophic bacteria account for ∼25% (14–40%; median and interquartile range) of the total nitrate uptake in surface waters with chlorophyll biomass <2 μg L−1. Estimates of new production computed from phytoplankton carbon uptake and f-ratios may be strongly overestimated in regions where nitrate uptake by heterotrophic bacteria is high and the biomass of phytoplankton is low.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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 source (direct Gemma or distilled Codex), 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".