The Sublethal Effects of Chemically-Dispersed Access Western Blend and Cold Lake Blend Diluted Bitumen on Rainbow Trout Embryos (Oncorhynchus mykiss)
Bibliographic record
Abstract
An increased demand for Canadian diluted bitumen has resulted in new proposals, such as the Enbridge Northern Gateway pipeline, for transportation to coastal ports for shipment to foreign markets. Access Western Blend (AWB) and Cold Lake Blend (CLB) are identified as the highest-volume dilbit products currently shipped in Canada, each with varying physical properties and chemical compositions. Though dilbit is similar to conventional crude oils in physical properties, the volatility of polycyclic aromatic hydrocarbons (PAHs) present in dilbit during oil spill scenarios causes changes to its environmental fate and behavior. This study characterizes the physiological effects of rainbow trout (Oncorhynchus mykiss) embryos in response to chemically-dispersed dilbit to establish salmonid sensitivity for populations at risk from dilbit spills caused by transportation or pipeline failures. Embryos were exposed for 23 days to dilutions of chemically-enhanced water accommodated fractions of AWB and CLB dilbit. Toxicity was determined by measuring mortality rate as well as the development of blue sac disease (BSD) in embryos at the end of the 23-day exposure. Physiological effects were assessed through mortality, prevalence of malformations, and measurement of gene transcripts associated with phase I (cyp1a), phase II (hsp70, gst, gpx, nfe2, gsr, sod, cat), xenobiotic metabolism (ahr, arnt), and cell cycling and mutation response (p53). Complete mortality was observed at the highest treatments of 1 % v/v due to dispersant toxicity. Malformations were measured in the second highest treatments (0.1 % v/v) of AWB and CLB dilbits. Significant changes in gene expression were observed in ahr, cyp1a, gsr, p53, and sod1 in response to the upper nominal loadings of CEWAF dilbits. This is the first study on the physiological effects of chemically-dispersed dilbit exposure in a native Canadian fish species and may provide a baseline of physiological effects for other economically-important salmonids with varying life strategies and environmental sensitivities.
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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 | 0.000 | 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) | 0.001 | 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".