Exploring the hydrogeological functioning and microbial habitats of the deep hillslope aeration zone in limestone-mudrock alternations
Bibliographic record
Abstract
The aeration zone beneath topographic groundwater recharge areas, comprising variably water-saturated soil, regolith and bedrock is a typically large but hardly explored compartment of the Critical Zone. Fluid and matter exchange within the deep hillslope aeration zone, the dynamics of its diverse microbial dwellers and their contribution for subsurface matter cycling and groundwater quality are widely unknown. In the Hainich Critical Zone Exploratory (Collaborative Research Center AquaDiva, Küsel et al., 2016), we accessed the aeration zone and groundwater resources in fractured limestone-mudstone alternations by exploratory drillings and hillslope monitoring wells. Multi-year groundwater sampling, environmental monitoring, drill core and petrological analyses revealed a multi-storey architecture of the aeration zone, covering perched water bodies and multi-directional flow phenomena (Lehmann and Totsche 2020). In a ~50 m deep well that underwent pronounced seasonal head fluctuation up to 25 m of oligotrophic groundwater, we incubated bedrock fragments that mimicked large fracture habitats and monitored the dynamic environmental conditions in the fractured mixed carbonate-/siliciclastic alternations as well. During groundwater-saturated colonization, successional exposure to seasonal de-saturation and re-saturation, we analyzed the bacterial and archaeal 16S rRNA diversity and found a diverse bacterial, and less diverse archaeal community, both including persistent genera that withstood the harsh environmental changes. In accordance with mature fracture-surfaces (drill cores), the colonized rock fragments were dominated by Gammaproteobacteria. General compositional differences to communities within the phreatic zone (i.e. groundwater and rock matrices), and shallow sources in soil, suggest a distinct subsurface microbiome that is hardly represented by ecological surveys that utilize groundwater or rock samples. References: Küsel, K., Totsche, K. U., Trumbore, S. E., Lehmann, R., Steinhäuser, C., Herrmann, M. (2016). How deep can surface signals be traced in the critical zone? Merging biodiversity with biogeochemistry research in a central German Muschelkalk landscape. Frontiers in Earth Science 4 (32). https://doi.org/10.3389/feart.2016.00032 Lehmann, R., Totsche, K. U. (2020). Multi-directional flow dynamics shape groundwater quality in sloping bedrock strata. Journal of Hydrology 580. https://doi.org/10.1016/j.jhydrol.2019.124291
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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 | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".