Assessing natural recovery from contaminants in a river using sediment chemistry and toxicity from different depth ranges
Bibliographic record
Abstract
To determine whether natural recovery was occurring in a depositional area of the St. Marys River (Ontario, Canada) known as East Bellevue Marine Park (EBMP), sediment was collected from two depth ranges, 0-5 cm and 0-10 cm, and subjected to a series of laboratory toxicity tests and chemical analysis. Toxicological responses (survival, growth, reproduction, development) of four benthic invertebrates and the fathead minnow were compared at test vs. reference sites using univariate and multivariate (ordination) techniques. Temporal trends in sediment chemistry and invertebrate toxicity were examined with time series data from 2008 through to 2018. Polycyclic aromatic hydrocarbons (PAHs; ≤ 37 mg/kg) and petroleum hydrocarbons (PHCs; ≤ 6266 mg/kg) were elevated in EBMP compared to reference sites (PAHs, ≤ 1.6 mg/kg; PHCs ≤ 180 mg/kg). Comparatively, the 0-5 cm sediment layer had lower concentrations of all contaminants than the 0-10 cm layer at three of four test sites. Over time, contaminant concentrations have mostly remained stable or have decreased. There were no significant differences in survival, growth, or development of the larval fish in EBMP compared to the upstream reference sites, and no differences between sampling depths. However, most EBMP sediments were toxic to invertebrates, driven by reduced reproduction by the worm Tubifex and reduced survival by the amphipod Hyalella. Among habitat variables, a combination of different classes of compounds based on ordination scores (PHCs, oil and grease, metals) was most strongly correlated to toxicological response. There was little to no difference in toxicity between sampling depths based on integrated endpoint response; however, individual endpoints showed mostly greater toxicity from exposure to the 0-10 cm layer. Over time, toxicity has mostly remained stable or showed improvement. These results provided some positive indications that gradual natural recovery is occurring in EBMP.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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".