The importance of transparent exopolymer particles over ballast in determining both sinking and suspension of small particles during late summer in the Northeast Pacific Ocean
Bibliographic record
Abstract
Gravitational sinking of particles is a key pathway for the transport of particulate organic carbon (POC) to the deep ocean. Particle size and composition influence particle sinking velocity and thus play a critical role in controlling particle flux. Canonically, sinking particles that reach the mesopelagic are expected to be either large or ballasted by minerals. However, the presence of transparent exopolymer particles (TEP), which are positively buoyant, may also influence particle sinking velocity. We investigated the relationship between particle composition and sinking velocity during the Export Processes in the Ocean from RemoTe Sensing (EXPORTS) campaign in the Northeast Pacific Ocean using Marine Snow Catchers. Suspended and sinking particles were sized using FlowCam for particle imaging, and their biogeochemical composition was assessed by measuring the concentration of particulate organic carbon (POC) and nitrogen, particulate inorganic carbon, biogenic and lithogenic silica, and TEP. Sinking fluxes were also calculated. Overall, both suspended and sinking particles were small (<51 μm, diameter) in this late summer, oligotrophic system. Contrary to expectation, the ratio of ballast minerals to POC was higher for suspended particles than sinking particles. Further, suspended particles showed TEP-to-POC ratios three times higher than sinking particles. These ratios suggest that TEP content and not ballast dictated whether particles in this system would sink (low TEP) or remain suspended (high TEP). Fluxes of POC averaged 4.3 ± 2.5 mmol C m−2 d−1 at 50 m (n = 9) and decreased to 3.1 ± 1.1 mmol C m−2 d−1 at 300–500 m (n = 6). These flux estimates were slightly higher than fluxes measured during EXPORTS with drifting sediment traps and Thorium-234. A comparison between these approaches illustrates that small sinking particles were an important component of the POC flux in the mesopelagic of this late summer oligotrophic system.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".