Trapped river otters (Lontra canadensis) from central Saskatchewan exhibit differences in total and organic mercury concentrations with sex and geographic location
Bibliographic record
Abstract
Human activities have resulted in increasing amounts of mercury Hg(II) in the atmosphere, oceans, and terrestrial systems. Biological processes convert inorganic forms of mercury released into the atmosphere into the neurotoxic and bioaccumulating methylmercury (MeHg) species resulting in increased concern for Hg emissions entering the biosphere. Once deposited from the atmosphere, in-situ methylation of inorganic Hg in sediments is believed to be the largest source of MeHg to freshwater aquatic systems compared to input from the terrestrial environment (i.e. run-off) or atmospheric deposition. Methylation of Hg is predominantly a microbial mediated process that is facilitated by some sulfate and iron reducing bacteria, as well as methanogens. Biological activity, nutrient availability, pH, temperature, redox potential, and the presence of inorganic and organic complexing agents have significant effects on rates of methylation. Degradation of MeHg can occur as well, so that the amount of MeHg available to organisms is a result of two opposing processes. Mink (Mustela vison) and otter (Lontra canadensis) are the most studied mammalian wildlife species with regard to Hg exposure and toxicity. Data indicate that consumption of diets that contained Hg (as MeHg) >1 mg kg-1 wet weight can cause neurotoxicity and death in adult mink and otter. Neurological signs in MeHg-intoxicated mammals typically include lethargy, ataxia, limb paralysis, tremors, convulsions, and ultimately death. Here, I measured Hg concentrations in fur, liver and kidney tissues removed from river otters (Lontra canadensis) collected from trappers in central Saskatchewan (n = 203) over two trapping seasons. Total Hg (THg) concentrations measured in otter tissues were consistent with tissues measured in other non-impacted sites in Canada. Fur THg was positively correlated with total and organic Hg measured in liver and kidney tissue, highlighting the potential for using fur as a rapid and less expensive method of monitoring Hg in mammals. Livers from males had significantly higher mean organic Hg concentrations than livers of females (p = 0.015), however, no sex related differences were observed in kidney organic Hg concentrations. Total Hg concentrations in the fur of otters collected in the Churchill River Upland (Boreal Shield ecozone) was significantly higher (p < 0.001) than otters collected from all other ecoregions located in the Boreal Plain ecozone. Otters trapped in close proximity to the now decommissioned smelter located in Flin Flon, MB contained the highest concentrations of total Hg measured in my study.
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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 | 0.000 | 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 | 0.001 |
| 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 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".