Size‐dependent community patterns differ between microbial eukaryotes and bacteria in a permafrost lake–river–sea continuum
Bibliographic record
Abstract
Abstract Microbial communities play a crucial role in ecosystem functioning, with contributions that can vary among taxonomic domains and size fractions. However, microbial assembly processes for bacteria and eukaryotes are seldom characterized together using size fractionation, especially in flowing waters. Here, we used amplicon sequencing combined with physicochemical measurements to determine how size fractionated (small fraction 0.22–3 μ m; large fraction > 3 μ m) community structure and diversity varied over a subarctic river continuum. We sampled the Sheldrake River, a 25 km river flowing through degrading discontinuous permafrost, from its lacustrine source through subarctic forest shrub tundra to its discharge plume in eastern Hudson Bay (Nunavik, Canada). Microbial community structure differed by size fraction and among habitats, with differences in the variables potentially driving community structure among size fractions and microbial domains. For the small size fraction, colored dissolved organic matter was a significant covariate of community variation for both bacteria and eukaryotes, consistent with the influence of landscape gradients. There were contrasting diversity patterns along the lake–river transect between bacterial size fractions. An abundance‐based approach indicated that for all communities, assembly processes were dominated by homogeneous selection, while an incidence‐based method showed dominance of heterogeneous selection for bacteria and homogenizing dispersal for microbial eukaryotes. Our findings show how different components of riverine microbial communities can have divergent patterns along the downstream continuum to the sea.
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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 | 0.001 |
| 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".