Methane and methylmercury production potentials in North Carolina Piedmont stream sediments
Bibliographic record
Abstract
Methylated mercury (MeHg) is produced by sulfate reducing bacteria (SRB), iron reducing bacteria (FeRB), methane producing Archaea (MPA), and other microbes under anaerobic conditions. These microbial groups compete for substrates including hydrogen and acetate. SRB are able to outcompete other anaerobic microbes when sulfate is in excess. However, low concentrations of sulfate in streams are thought to reduce the metabolic importance of SRB in streams. Although SRB are regarded as the primary producers of MeHg in many aquatic environments, it may not be universal. MPA have been implicated as the primary producers of MeHg in periphyton in a Canadian fluvial lake. Suppression of methanogenesis by SRB and the potential contributions from SRB, MPA and other MeHg producing microbes (including FeRB) to the production of MeHg in stream sediments was evaluated. Lower methanogenesis rates occurred if SRB were not inhibited, but methane production significantly increased if SRB were inhibited. These data suggest SRB reduce methane production, and are potentially the primary producers of MeHg. Other MeHg producing microbes (i.e., FeRB) contributed less than SRB to MeHg production. MPA produced MeHg in negligible amounts. This suggests that Hg methylation in sediments examined in this study was mediated primarily by SRB. This additionally suggests that microbes other than SRB may perform the majority of mercury methylation in the absence of SRB. Availability of sulfate and electron acceptors likely determines the relative importance of these microbial groups and thus pathways of Hg methylation in natural stream conditions.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 |
| 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".