Stable carbon, nitrogen, and sulfur isotope ratios in riparian food webs on rivers receiving sewage and pulp-mill effluents
Bibliographic record
Abstract
We examined spatial trends in ratios of stable isotopes of nitrogen (δ15N), carbon (δ13C), and sulfur (δ34S) in riparian food webs leading to a riparian, insectivorous bird species, the tree swallow (Tachycineta bicolor), on rivers receiving pulp-mill effluent and municipal sewage and compared them with ratios of these isotopes in components of the effluents themselves. The study was conducted on two rivers in western Canada at sites upstream and downstream from sewage and pulp mill effluent sources. Municipal sewage contained materials with δ15N or δ13C values that were distinct from background conditions in the receiving environment. Pulp-mill effluent contained materials with δ34S values that were distinct from those at upstream sites on the rivers. At both locations, effluent-derived nitrogen and sulfur were observed in algae and suspended sediments at sites downstream from the effluent sources. This was also observed in adult aquatic insects, the one exception being that uptake of effluent-derived nitrogen was detected isotopically at only one location. Tree swallows' use of sewage-derived nitrogen was evident only at one location, while use of pulp-mill-derived sulfur was evident only at the other location. Our study demonstrates the usefulness and limitations of measuring stable isotopes for tracing the movement of nutrients derived from sewage and pulp-mill effluent in freshwater ecosystems and, further, indicates that such tracing may be extended to riparian species feeding on aquatic prey.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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".