Toxicity of surface water and pore water from an oil sands pit lake (Lake Miwasin) to Daphnia
Bibliographic record
Abstract
Canada holds approximately one-third of the world's confirmed crude oil reserves, primarily concentrated in the Alberta Oil Sands (AOS) region, in the form of bitumen. However, the extraction process of oil sands generates significant volumes of tailings and process water, which raises concerns about their potential effects on aquatic life and the need for remediation. Lake Miwasin, constructed in 2018, serves as a pilot-scale pit lake and a model for this context. It features treated fluid tailings overlaid by a mixture of oil sands process-affected water (OSPW) and freshwater, exhibiting seasonal stratification. Since its establishment, Lake Miwasin has been colonized by various organisms, including the Crustacean, Daphnia pulex. Monitoring data from Lake Miwasin has shown the presence of compounds in both water and sediment that could be detrimental to aquatic organisms. Therefore, the primary goals of this research were to assess surface water and pore water toxicity, including an evaluation of selenium (Se) bioaccumulation in Daphnia species exposed to the conditions representative of Lake Miwasin at its early development stages and possibly other future pit lakes in the AOS region.\nThis study examined the toxicity of Lake Miwasin surface water (LMW) and pore water (LMP) using lab-cultured and native Daphnia species. Interestingly, LMW exhibited no acute or chronic toxicity towards D. magna and D. pulex (lab strains) and the native Daphnia sp. (collected from Humboldt Lake, SK, Canada). However, LMP demonstrated acute toxicity to both lab strains and the native D. pulex (collected from Lake Miwasin, AB, Canada). Lake Miwasin pore water also negatively impacted lab D. pulex reproduction, leading to a reduced number of offspring. Salinity emerged as a significant stressor in LMP, and a Toxicity Identification Evaluation (TIE) phase I suggested ammonia and metals in LMP as potential contributors to the observed toxicity in the tested organisms. On a related point, results showed that concentrations of dissolved Se in LMW from 2019 to 2021 exceeded the Canadian Council of Ministers of Environment (CCME) water quality guidelines for long-term aquatic life protection (1 µg/L), and the British Columbia Ministry of Environment (BC MoE) water guideline alert concentration for the protection of aquatic life (1 µg/L). The latter water guideline was also adopted by the Government of Alberta. Further, another experiment assessed Se bioaccumulation in D. pulex through dissolved and dietary exposure routes, drawing comparisons to native specimens collected from Lake Miwasin. In semi-static tests (12 days), lab strain D. pulex exposed to selenate [Se(VI)] showed a Se concentration-dependent increase from days 5 to 12 for most treatments, whereas a lower bioaccumulation occurred at higher Se concentrations, which suggests a potentially internal regulatory mechanism. Native D. pulex exposed to LMW in laboratory conditions showed that Se bioaccumulation levels were similar to those of D. pulex collected directly from Lake Miwasin. Despite these findings, the Se concentrations in D. pulex from both lab exposures and Lake Miwasin collections remained below available regulatory guidelines for invertebrate tissue (4 µg/g), suggesting that D. pulex appears to pose minimal risk as a food source in the Lake Miwasin ecosystem. \nThese findings provide useful insights into the toxicity of Lake Miwasin water to aquatic invertebrates, the potential for Se bioaccumulation in daphnids in Lake Miwasin, the potential enhancement of pit lake monitoring programs, and the decision-making regarding the use of end pit lakes in the reclamation of OSPW and oil sands tailings.
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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".