Dissolved Nitrogen Cycling in the Eastern Canadian Arctic Archipelago From Stable Isotopic Data
Bibliographic record
Abstract
Climate change is expected to drastically alter the input of inorganic nitrogen (N) sources in the Eastern Canadian Arctic Archipelago (ECAA) with increasing discharge from glacial meltwater and permafrost thawing. Since dissolved inorganic N is generally depleted in surface waters, dissolved organic N (DON) could represent a significant source of nutrients limiting primary production in Arctic ecosystems. Yet, few DON data for this region exist. We analyzed stable isotopes (δ15N and δ 18O of DON and NO3-) to investigate dissolved nitrogen cycling in glacial rivers and marine surface samples collected in the ECAA during summer 2019. We used isotopic data to determine dissolved N sources as well as production and consumption processes. DON concentrations (0.54-11.61 μmol L-1) and δ15N of DON (-0.71-9.61 ‰) in the ECAA were variable between different locations, suggesting the occurrence of different processes. DON concentrations were low in most rivers (up to 4.89 μmol L-1). DON concentrations versus salinity fell along a mixing line between low DON riverine and higher DON marine end members. Thus, increased input from glacial meltwater in the ECAA could act to increase stratification and dilute the marine DON pool, ultimately affecting primary productivity. In regions of highest primary productivity, DON concentrations were inversely correlated with chlorophyll-a and the δ15N of DON, suggesting net DON consumption during these localized phytoplankton blooms. We derived an isotope effect of -6.9‰ during DON consumption. Our data helps establish a baseline to assess future change in nutrient regime for this climate sensitive region.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".