Intraspecific variation in a dominant prey species can bias marine predator dietary estimates derived from stable isotope analysis
Bibliographic record
Abstract
Abstract It is often assumed that variation in consumer stable isotope values ( δ 15 N and δ 13 C) reflect shifts in diet between isotopically distinct prey species. However, an alternate hypothesis is that such variation could be as a result of spatial, temporal, or ontogenetic variation in the stable isotope values of a key prey species that propagate up marine food chains. In the Southern Ocean, Antarctic krill ( Euphausia superba ) occupy a key position, linking primary production to secondary consumers including fish, squid, seabirds, and marine mammals. As such Antarctic krill represent an ideal prey species to test the critical assumptions behind what has become a common method of dietary analysis in marine predators. Similar to previous studies, we found that stable isotope values of Antarctic krill exhibit significant intraspecific variation associated with both ontogenetic (size) and oceanographic factors (chlorophyll a concentration). Our modeling results showed that intraspecific variation in the stable isotope values of Antarctic krill has the potential to force mean isotope values of krill predators by as much as 2.4‰, independent of changes in the species composition of diet. Our findings indicate that intraspecific variation in the stable isotope values of a single, dominate prey species, such as Antarctic krill, has the potential to bias both absolute and relative estimates of marine predator diets using stable isotope mixing models. Therefore, caution is warranted to avoid spatial, temporal, and ontogenetic mismatches between the stable isotope values of prey sources used in mixing models and the actual stable isotope values of prey consumed by marine predators.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| 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) | 0.005 | 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".