Short-term response to watershed logging on biomass mercury and methylmercury accumulation by periphyton in boreal lakes
Bibliographic record
Abstract
In the boreal forest, watershed logging may increase runoff as well as chemical loading, including nutrient, dissolved organic carbon and mercury, to lakes. Since they are exposed directly to nutrients and contaminants exported from the watershed, littoral communities such as periphyton may respond quickly to watershed disturbances. The objectives of this study were to evaluate the response of periphyton to watershed logging using a BACI (Before/After Control, Impact) statistical approach, and to develop a predictive tool to facilitate the elaboration of practical logging policies aimed at reducing Hg loading to lakes. In this study, we compare the periphyton biomass as well as their total mercury and methyl-mercury levels in 18 boreal Canadian shield lakes. During the ice-free season from 2000 to 2002, eight lakes were monitored before and after logging whereas the others served as controls. The BACI statistical analyses reveal a significant impact of logging on periphyton biomass (decrease; 0.6 to 1.5-fold) and methyl-mercury accumulation (increase; 2 to 9.6-fold). This study demonstrates that periphyton responds quickly to disturbances of the watershed. Our results suggest that the periphyton and watershed characteristics could serve as good management tools and logging should be limited in watersheds with a mean slope below 7.0%. / En forêt boréale, la coupe forestière peut augmenter l'écoulement et l'apport d'éléments chimiques aux lacs tel que le carbone organique dissous et le mercure. Les communautés littorales, comme le périphyton, peuvent être exposées directement aux apports de contaminants exportés du bassin versant, et ainsi répondre rapidement aux perturbations de ce dernier. Les objectifs de cette étude étaient d'évaluer la réponse du biofilm périphytique aux coupes forestières en utilisant une approche statistique de type BACI, et de développer des outils prédictifs utiles pour l'élaboration de politiques forestières visant la réduction des apports de Hg dans les lacs. Dans cette étude, nous avons échantillonné 18 lacs boréaux du bouclier canadien et comparé la biomasse et les concentrations de mercure total et méthyl-mercure du périphyton. Durant la saison libre de glace de 2000 à 2002, huit lacs ont été échantillonnés avant et après la coupe alors que les autres ont servi de témoins. Les analyses statistiques BACI révèlent un impact significatif des coupes sur la biomasse (diminution; 0.6 à 1.5 fois) et sur les concentrations de méthyl-mercure (augmentation; 2 à 9.6 fois). Cette étude démontre que le périphyton répond rapidement à une perturbation du bassin versant. Nos résultats suggèrent que le périphyton et les caractéristiques du bassin versant peuvent être de bons outils de gestion et que la coupe forestière devrait être limitée lorsque la pente moyenne est inférieure à 7.0%.
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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 | 0.000 | 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) | 0.000 | 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".