Stable hydrogen and oxygen isotopes in aquatic food webs are tracers of diet and provenance
Bibliographic record
Abstract
Summary The stable hydrogen and oxygen isotope ( δ 2 H and δ 18 O ) composition of animal tissues are well‐established tracers for terrestrial migration ecology and wildlife forensics. However, the behaviour of these isotopes in aquatic ecosystems and their potential as tracers of diet and provenance are complicated because of inputs from ambient H 2 O and diet. We conducted controlled aquaria‐based experiments to quantify the mechanisms that drive the H and O isotopic flow within and among aquatic species. The isotopic composition of water and diet of two aquatic species ( C hironomus tentans and P oecilia reticulata ), representing two trophic levels, was varied in six isothermal treatments. Both species were raised from juvenile to adult to ensure that tissues were in isotopic equilibrium with their dietary and environmental conditions (ambient water, food, dissolved oxygen). We measured water, dissolved O 2 , diet, tissue protein and lipids for δ 2 H or δ 18 O . The flows of H and O isotopes for tissue formation in aquatic organisms were parameterized using a steady‐state multi‐pool mass‐balance model. The ambient H 2 O contribution to tissue protein H and O isotopes in both species was significant (30–50% for 2 H and >80% for 18 O ). An apparent trophic effect for δ 2 H and isotopic discrimination between water and protein for δ 18 O ( c . 15 ‰) were identified. Our isotopic data and model revealed potential applications and cautions in using δ 2 H and δ 18 O measurements for ecological studies in aquatic food webs. Tissue δ 2 H values may be a complementary trophic tracer in aquatic food webs, but only when the main controlling mechanisms are properly accounted for (i.e., H isotopic exchange with water during protein synthesis and influence of metabolic water). Measurements of δ 18 O , on the other hand, reflect that of water and so can be used for predicting isotopic assignment to origin of aquatic organisms as there is no complicating trophic effect, but more δ 18 O field data and improved analytical precision may be required to better establish the strengths to ecological applications.
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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 | 0.001 | 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 | 0.000 | 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 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".