Emergence of <i>Prochlorococcus</i> in the Tonian oceans and the initiation of Neoproterozoic oxygenation
Bibliographic record
Abstract
Prochlorococcus are the smallest and most abundant photosynthetic organisms on Earth, contributing up to 50% of the chlorophyll in the oligotrophic oceans. Despite being important in regulating the carbon cycle in today's ocean, the ecological significance of Prochlorococcus in Earth's history remains elusive. Our new robustly calibrated molecular clock analysis reveals that Prochlorococcus emerged in the deep photic zone of the Tonian (1,000-720 Mya) oceans. The classical light-harvesting antenna complex in Cyanobacteria, i.e., the phycobilisome, was replaced in Prochlorococcus by the chlorophyll‐based antenna, enabling more efficient use of blue light that penetrates into deeper water. Importantly, Prochlorococcus colonization of deep water enhanced access to phosphate, which was abundant in upwelled seawater, but likely scarce in the Tonian surface ocean, promoting expansion of Prochlorococcus , displacement of incumbent low-light adapted anoxygenic photoferrotrophs, and associated increases in photosynthetic oxygen production. Colonization of deeper waters would also have improved access to ammonium, leading to the neutral loss of nitrate utilization genes. Our research thus documents the conspicuous emergence of new photosynthetic bacterial lineages in the run-up to the Neoproterozoic oxygenation event, implying an additional layer of eco-evolutionary complexity during this pivotal interval in Earth's history.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| 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".