An evaluation of stable nitrogen isotopes and polychlorinated biphenyls as bioenergetic tracers in aquatic systems
Bibliographic record
Abstract
This study investigated the relationship between stable nitrogen isotopes (δ 15 N) and polychlorinated biphenyl (PCB) concentrations in rock bass (Ambloplites rupestris) and bluegill sunfish (Lepomis macrochirus) with respect to age, size, and diet. δ 15 N signatures in both species exhibited enrichment with increasing size and approached steady state with respect to dietary δ 15 N values by the second year of growth. Young-of-the-year fish, however, exhibited lower nitrogen isotope enrichment over the diet, indicating that the commonly held trophic enrichment factor of 3.4 is more suitable for older, slow-growing individuals. PCB accumulation in both species progressed from being dominated by uptake from water in small (<100 g) fish to dietary uptake in larger individuals as a function of bioenergetic constraints such as food energy conversion and contaminant assimilation efficiencies. Significant increases in PCB accumulation were attributed to decreased specific growth rates such that ≤60% of body mass was gained on an annual basis. This effect was most noted in bluegills where higher PCB biomagnification factors were a consequence of increased foraging costs associated with an invertebrate diet. It is concluded that growth-related changes in species bioenergetics regulate both contaminant accumulation and δ 15 N dynamics.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| 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".