Modeling Studies of Antarctic Krill (<i>Euphausia superba</i>) Survival During Transport Across the Scotia Sea and Environs
Bibliographic record
Abstract
The Antarctic krill (Euphausia superba) populations at South Georgia, which is in the eastern Scotia Sea, are hypothesized to be sustained by import of individuals from upstream regions, such as the western Antarctic Peninsula. To test this hypothesis a modeling framework consisting of the Harvard Ocean Prediction System (HOPS) and a time-dependent, size-structured, physiologically-based krill growth model was developed. The simulated circulation fields obtained from HOPS were used with drifter studies to determine regions and pathways that allow transport of Antarctic krill to South Georgia. Pelagic phytoplankton concentrations along the simulated drifter trajectories were extracted from historical Coastal Zone Color Scanner measurements and sea ice algae concentrations were calculated from sea ice concentration and extent extracted along particle trajectories from Special Sensor Microwave/Imager measurements. As additional food sources, a time series of heterotrophic food was constructed from historical data, and time series of detritus concentrations along simulated drifter trajectories were calculated using phytoplankton concentrations extracted from Coastal Zone Color Scanner measurements together with measured particulate organic carbon to chlorophyll a ratios. These food resources, along specified drifter trajectories were then input to the krill growth model to determine the size and viability of krill during transport from the source region to South Georgia. The drifter simulations showed that krill spawned along the mid to northern portion of the west Antarctic Peninsula continental shelf, coinciding with known krill spawning areas, can be entrained into the Southern Antarctic Circumpolar Current Front and be transported across the Scotia Sea to South Georgia in 10 months or less. Drifters originating on the continental shelf of the Weddell Sea can reach South Georgia as well; however, transport from this region averages about 20 months. The krill growth model simulations showed that no Single food source, such as pelagic phytoplankton, detritus, sea ice algae, or zooplankton, can support continuous growth of Antarctic krill during the 168 to 225 days needed for transport from the western Antarctic Peninsula to South Georgia. However, combinations of the food sources during the transport time enhanced krill survival, with zooplankton (heterotrophic food) and detritus being particularly important during periods of low pelagic phytoplankton concentrations. The growth model simulations also showed that larval and juvenile krill originating along the western Antarctic Peninsula can grow to the 1+ (14 mm to 36 mm) and 2+ (26 mm to 45 mm) sizes observed at South Georgia during the time needed for transport to this region. The additional transport time needed by krill originating in the Weddell Sea allows retention in a potentially high food environment, provided by sea ice, for almost one year. The krill then complete transport to South Georgia in the following year and larval and juvenile krill grow to 2+ (26 mm to 45 mm) and 3+ (35 mm to 60 mm) sizes during transport.
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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 | 0.000 | 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 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".