Coupled shifts in DOM composition and microbial community structure lead to variable biodegradation rates in thermokarst-affected permafrost stratigraphies
Bibliographic record
Abstract
Permafrost thaw can drastically alter dissolved organic matter (DOM) composition within fluvial networks, and simultaneously affect the microbial communities that degrade DOM. However, it is unclear how coupled thaw-induced change in DOM and microbes might affect microbial decomposition of permafrost-origin DOM (biodegradation), and therefore possible mineralization to carbon dioxide. Here, we use a series of incubations to explore how biodegradation varies with DOM and microbe source, and how microbial community composition changes following incubation with thaw-origin DOM. We undertake this work using leachates from different stratigraphic units across a series of retrogressive thaw slumps on the Peel Plateau, Canada, and microbial communities from upstream of, and draining, slumps. DOM composition and biodegradation varied by stratigraphic unit and across sites that were only tens of kilometers apart, but situated along different recessional fronts of the Laurentide Ice Sheet. Permafrost leachates from paleo-active layers were generally more biolabile than leachates from deeper, unmodified tills, and both were more labile than active layer leachates. Biodegradation also tended to be slightly greater for incubations inoculated with microbes from unimpacted stream water. These results emphasize that permafrost thaw-derived DOM composition and biolability will vary across stratigraphic, landscape, and regional scales, and that the composition of the recipient microbial community may play a role in determining immediate DOM fate.
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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 | 0.000 |
| 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 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".