The Diatom Disconnect: Retention near surface waters limits carbon transfer to the deep ocean
Bibliographic record
Abstract
The Southern Ocean, a region highly vulnerable to climate change, plays a critical role in regulating global nutrient cycles and atmospheric CO₂ via the biological carbon pump. Diatoms, a group of photosynthetically active plankton with dense opal skeletons, are central to this process, as their exoskeletons are thought to enhance the transfer of particulate organic carbon to depth, making them main vectors of carbon storage. However, conflicting observations obscure the mechanistic link between diatoms, opal, and particulate organic carbon fluxes, especially in the twilight zone where the greatest flux losses occur.Here we present direct springtime flux measurements from different sectors of the subpolar Southern Ocean, demonstrating that across large areas of the subpolar twilight zone, carbon is efficiently transferred to depth: however, not by diatoms. Instead, opal is retained near the surface ocean, indicating that processes such as diatom buoyancy regulation and grazer repackaging can negate the ballast effects of diatoms’ skeletons. Using image data, we further reveal species-specific differences in diatom flux dynamics, highlighting the complexity of their role in the carbon cycle.Our findings challenge the assumption that diatom-rich surface waters are necessarily associated with effective carbon export and transport in the Southern Ocean. They suggest that shifts in phytoplankton community composition driven by climate change may have a smaller impact on biological carbon storage than current models predict.
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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 | 0.000 | 0.000 |
| 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) | 0.002 | 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".