Stable N and C isotopes in the organic matrix of fish otoliths: validation of a new approach for studying spatial and temporal changes in the trophic structure of aquatic ecosystems
Bibliographic record
Abstract
Stable isotope studies of long-term ecosystem change are often hampered by lack of archived tissue samples. Here, we provide a reliable method for extracting the organic matrix from fish otoliths, demonstrate differences in isotope values between the soluble and insoluble organic fractions, and provide the trophic enrichment factors (ε). The analyses were performed on otoliths from wild-caught adult Atlantic cod (Gadus morhua) and otoliths from a 6-month diet-switch experiment with juvenile cod. Acid hydrolysis of otolith powder followed by ultrafiltration enabled us to purify and separate the soluble and insoluble organic material. There was a significant 1.72‰ and 0.15‰ difference in δ 15 N and δ 13 C, respectively, between the soluble and insoluble organic fraction of the otolith. This emphasizes the need for separation of the two fractions before analysis. The diet-specific trophic enrichment (ε otolith-diet ) in the soluble fraction varied between −0.20‰ and 0.31‰ for nitrogen and between 0.09‰ and 0.23‰ for carbon. In conclusion, the organic matrix of otoliths provides an attractive archive of organic material for ecological stable isotope analysis that has the potential to provide important insights into historic changes in the trophic structure of aquatic ecosystems.
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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 | 0.000 |
| 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) | 0.000 | 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".