A three year time-series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a Northwestern Atlantic fjord
Bibliographic record
Abstract
Abstract. We report weekly observations of volatile organic iodocarbons (CH3I, CH2ClI and CH2I2) over the time-period May 2015 to December 2017 from 4 depths in Bedford Basin, a coastal fjord (70 m deep) on the Atlantic coast of Canada. The fjord is subject to winter-time mixing, seasonal stratification and bloom dynamics, subsurface oxygen depletion, local input of freshwater and occasional intrusions of higher density water from the adjacent continental shelf. Near-surface concentrations showed strong seasonal and sub-seasonal variability which is compared with other coastal time-series. Relationships with other properties lead to the hypothesis that near-surface iodocarbon production is linked to reduction of iodate to iodide under conditions of post-bloom phytoplankton senescence, nutrient stress or viral lysis following seasonal disappearance of nutrients. The vertical variation of CH2I2 and CH2ClI within the upper 10m is consistent with rapid photolysis of CH2I2. Average annual sea-to-air fluxes (62 nmol m−2 day−1) of total volatile organic iodine were slightly higher than observed in other coastal and shelf time-series and polyiodinated compounds contributed 85 % of the total flux. Fluxes were subject to strong interannual variability (2–3X) as a result, mainly, of wind-speed variability. Near-surface net production of CH3I averaged 1.0 pmol L−1 day−1 and was similar to rates in the English Channel but an order of magnitude higher than in shallow waters of the Kiel Fjord, Germany, possibly due to higher microbial degradation in the latter. The near-bottom (60 m) time-series showed evidence for CH3I production associated with organic matter degradation, and a possible switch from production of CH3I via an alkylation pathway to production of CH2I2 by a haloform-type reaction. Near-bottom CH3I production varied strongly between years but was generally ca. 20 times lower than near-surface production. Post-intrusion decreases of iodocarbons at 60 m suggested removal timescales of 14, 65 and 70 days for CH3I, CH2I2 and CH2ClI respectively.
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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 | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 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".