Visual predators and the diel vertical migration of copepods under Arctic sea ice during the midnight sun
Bibliographic record
Abstract
Despite the midnight sun, herbivore copepods Calanus hyperboreus, C. glacialis and Pseudocalanus acuspes displayed a normal diel vertical migration (NDVM) under the ice cover of Barrow Strait in spring, ascending into the chlorophyll-rich under-ice surface layer around maximum relative rate of change in irradiance (ΔI/I) at dusk but returning to depth a few hours later, well in advance of the dawn maximum ΔI/I. Nauplii prey being abundant above 50 m, the upward night-time incursions of the omnivore Metridia longa seldom reached beyond <25 m. In the absence of UV-B radiation or a temperature gradient, migration out of the euphotic layer was interpreted as a reaction to visual predators (e.g. Arctic cod Boreogadus saida and the hyperiid amphipod Themisto libellula). Swarms of T. libellula actively preying on copepods accumulated at the ice–water interface at dusk. Low vulnerability to visual predators and a more uniform vertical distribution of their food explained the limited DVM of the small omnivores Microcalanus pygmaeus, Oithona similis and Oncaea borealis. Once the feeding migrations developed, the daytime depth of the centre of mass of the distribution of a copepod was correlated to its size (r2 = 0.63). Our observations suggest that, under Arctic sea ice, interspecific differences in the pattern and extent of copepod DVM can be related to the vertical distribution of potential food and to vulnerability to visual predators.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.002 | 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".