Establishing realistic management objectives for urban lakes using paleolimnological techniques: an example from Halifax Region (Nova Scotia, Canada)
Notice bibliographique
Résumé
To determine pre-disturbance limnological conditions, evaluate the impact of environmental stressors (surface water acidification, nutrient inputs, climate change, and winter deicing salt), and set realistic recovery targets for lake management strategies, a rapid assessment paleolimnological approach was used to determine the amount (and likely causes) of environmental changes over the past ∼100–150 years in 51 urban lakes from Halifax, Nova Scotia (Canada). Diatom assemblages from lake sediment cores were used with “top” (recently deposited, surface) samples being matched to measured limnological conditions, and “bottom” (generally from >15 cm deep) samples used to infer pre-disturbance limnological conditions such as pH, total phosphorus (TP), specific conductance, and shifts due to changing climatic conditions. Environmental change was assessed by calculating the metric of change in species composition between present-day and pre-disturbance diatom assemblages, and inferences from quantitative estimates of diatom-inferred pH, specific conductance, and TP. All 51 study lakes have experienced floristic changes in diatom species composition since pre-disturbance times, but different environmental stressors were implicated: 8 of the 51 lakes underwent significant (i.e., >2 times the root mean-squared error [2X RMSE] of the inference model) decreases in diatom-inferred pH; 8 lakes had significant increases in diatom-inferred TP; and 19 otherwise relatively pristine lakes had increases in planktonic taxa consistent with observations linked to changes in lake seasonality and limnological changes most closely linked to climate warming in Nova Scotia and other regions. The remaining 16 lakes did not have large and consistent changes in diatom flora or changes in diatom-inferred TP or pH >2X RMSE of the prediction of the models. Lake-specific factors were related to these inferences, and the lakes that acidified were mainly the currently most acidic sites, whereas those that experienced issues related to eutrophication were generally among the most alkaline sites. Of our 51 lakes, 22 (including some experiencing pH, TP, or showing floristic changes linked to climate changes) had increases in measured conductivity (1980–2002) and, correspondingly, increased relative abundances of halophilic diatom taxa. These lakes, often with catchments containing high surface areas of impervious surfaces, are examples of a trend of increasing salinity in northeastern North American lakes likely related to winter application of deicing (road) salt. The application of this paleolimnological approach enabled us to identify which lakes have undergone significant changes in diatom assemblages, as well as which environmental stressor(s) were most probable. This information can help lake managers develop more targeted and effective management strategies.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».