Bibliographic record
Abstract
Photic-zone euxinia (PZE) is associated with several times in Earth's history including Phanerozoic extinction events and long parts of the Proterozoic. One of the best modern analogues for extreme PZE is Mahoney Lake in British Columbia, Canada where a dense layer of purple sulfur bacteria separate the oxic mixolimnion from one of the most sulfidic monimolimnions in the world. These purple sulfur bacteria are known to produce the carotenoid okenone. Okenone's diagenetic product, okenane, has potential as a biomarker for photic-zone euxinia, so understanding its production and transport is important for interpreting the geologic record. In the following dissertation, I examine Mahoney Lake with a multi-proxy approach. I use lipid biomarkers to understand organic matter production burial in the lake and find strong evidence of lateral transport of organic matter from shoreline microbial mats to the lake-bottom sediments. I also find evidence of okenone production in these shoreline mats and a carotenoid previously unreported in the environment, Thiothece-484, associated with the okenone synthetic pathway. Finally, I develop a new bioinformatics method to examine high-throughput metagenomic data and use this method to start understanding how the metabolic and lipid synthetic pathways of microbial communities in the lake are associated with each other.
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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 | 0.000 |
| 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".