Carbon cycling and redox chemistry in an anoxic marine basin, Bras d’Or Lake, Nova Scotia
Bibliographic record
Abstract
Measurements of oxygen, methane, pCO2, total dissolved inorganic carbon, total alkalinity, sulphide and nutrients were made in June, October and December 2017 in Whycocomagh Bay, a small marine basin at the western end of the Bras d’Or Lake estuarine system in Cape Breton, Nova Scotia. Dissolved oxygen was absent in the deep basin, similar to observations made in the years 1974, 1995-1997, and 2009-2021. Profiles of total dissolved inorganic carbon and total alkalinity were largely consistent with the sulphate reduction of particulate organic matter, having a Redfield stoichiometry of 106C:16N:1.6P. The concentration of dissolved methane ranged between 19-35 nmol L-1 (727-1147% saturation) above the thermocline, and reached 34.74 µmol L-1, (931,900% saturation) in the deep anoxic zone. The potential rate of microbial methane oxidation at the base of the oxycline, determined from an incubation experiment, was 0.34 µmol L-1 d-1, potentially acting to mitigate the flux of methane to the atmosphere. Deep water H2S concentrations ranged from 747 to 1,074 µmol L-1, more than a tenfold increase since the 1995-1997 study, with substantial increases also in ammonium and phosphate concentrations, likely as a result of eutrophication over the last two decades. Whycocomagh Bay presents an opportunity to study extreme marine redox chemistry at an easily accessible site.Keywords: Anoxic, methane, carbon cycle, carbon dioxide
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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 | 0.000 | 0.000 |
| 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) | 0.001 | 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 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".