Influence of vitamin B12 availability on oceanic dimethylsulfide and dimethylsulfoniopropionate
Bibliographic record
Abstract
Environmental context Cobalamin, or vitamin B12, is receiving increased attention as a critical trace nutrient in the growth and metabolic processes of oceanic phytoplankton and bacterial communities. We present evidence that indicates B12 has a more significant role in the biogeochemical cycling of the climatically important compounds dimethylsulfide and dimethylsulfoniopropionate than previously understood. Several possible mechanisms are examined that link cellular-level processes involving B12 to global-scale biogeochemical processes involving the oceanic cycling of dimethylsulfoniopropionate and dimethylsulfide. Abstract Evidence is presented showing that dissolved dimethylsulfoniopropionate (DMSPd) and dimethylsulfide (DMS) concentrations are influenced by the availability of vitamin B12 in two oceanographically distinct regions with different DMS production capacities, the central equatorial Pacific Ocean and the Ross Sea, Antarctica. In both locations, addition of B12 to incubation experiments resulted in decreases in DMS and, in some cases, DMSPd concentrations relative to unamended controls. In no case did increasing iron availability significantly (a = 0.1) alter DMS concentrations relative to controls. The relative decreases in DMS between B12 addition and control experiments were significant (a = 0.1) in five of seven experiments conducted at ambient iron levels. Overall, DMS concentrations were on average 33.4 % (±15.1 %; 1 standard deviation) lower, relative to unamended controls, by the end of incubation experiments when B12 was added. Declines in DMSPd were observed in three of five experiments. Similar trends were observed when B12 was added to iron-supplemented bottle incubation experiments (30.4 ± 10.4 % lower final DMS concentrations in +B12Fe treatments relative to +Fe treatments). Several possible molecular-level explanations exist for this link between B12 and DMS production, including potential B12 dependence of methyltransferase enzymes involved in both DMS and DMSP degradation. Although the enzymology of these reactions remains unclear, the relationships described here provide evidence for plausible mechanisms behind the microbial modulation of oceanic DMS.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 teacher head, 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".