Microbial Diversity and Biogeochemistry of a Shallow Pristine Canadian Shield Groundwater System
Bibliographic record
Abstract
An investigation was conducted to assess the microbial diversity and biogeochemistry of a pristine shallow glaciofluvial groundwater system on the Canadian Shield. Vadose zone sands were very fine-grained, consisting mostly of iron oxide-coated quartz. Below the water table in the saturated zone, iron oxide-coating on quartz grains were absent, owing presumably to reductive dissolution by Fe(III)-reducing bacteria and chemical weathering, respectively. Groundwater pH was circumneutral at 6.4 + 0.1, and Eh was slightly reducing at 349 ± 15 mV compared to local surface waters at 417 ± 21 mV; the total dissolved solids concentration in groundwater was 45.2 ± 6.9 mg/L. A total of 269 clones were sequenced and compiled into a 16S rRNA gene library, and representative operational taxonomic units (OTU) were retrieved from basic local alignment search tool (BLAST) analyses at the species-level across 7 phyla, including Acidobacteria, Actinobacteria, Bacteroidetes, Chlorobi, Firmicutes, Planctomycetes, and Proteobacteria. Aerobic, anaerobic, and facultative anaerobic heterotrophs were predominant among the OTU. Lithoautotrophic ammonium- and nitrite-oxidizers were especially prominent, as were diazotrophs, nitrate- and nitrite-reducers. Representative OTU also included Fe(II)-oxidizers and Fe(III)-reducers, whereas those associated with sulfur cycling were rare. These observations suggest that there is considerable potential for biogeochemical cycling of nitrogen and iron within shallow glaciofluvial groundwater systems on the Canadian Shield.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 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".