| Titre | Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
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| Auteur | Hutchinson, S J; Hamilton, P B; Patterson, R T; Galloway, J M ; Nasser, N A; Spence, C; Falck, H |
| Source | PeerJ 7, 6269, 2019 p. 1-21, https://doi.org/10.7717/peerj.6269  Accès ouvert |
| Image |  |
| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20180371 |
| Éditeur | PeerJ |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.7717/peerj.6269 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Territoires du Nord-Ouest |
| SNRC | 85J/09SW |
| Région | Pocket Lake; Yellowknife |
| Lat/Long OENS | -114.3833 -114.3667 62.5167 62.5000 |
| Sujets | Holocène; paléoécologie; eaux de surface; lacs; biote; microfossiles; algues; diatomées; assemblages fossiles; carottes de sediments lacustres; antécédents tectoniques; volcanisme; cendre volcanique;
antecedents de sedimentation; milieu sédimentaire; milieux lacustres; datation radiométrique; datation au radiocarbone; distribution stratigraphique des fossiles; analyses stratigraphiques; biostratigraphie; peuplements biologiques; écosystèmes;
effets sur l'environnement; acidité; paléoclimats; sédiments lacustres; Résilience; Adaptation à l'environnement; géologie de l'environnement; géologie des dépôts meubles/géomorphologie; paléontologie; géochronologie; stratigraphie; Phanérozoïque;
Cénozoïque; Quaternaire |
| Illustrations | cartes de localisation; cartes géolscientiques généralisées; tableaux; modèles; photographies; profils; graphiques; diagrammes biostratigraphiques |
| Programme | Géosciences environnementales Exploration minérale: conditions de base au nord |
| Diffusé | 2019 01 25 |
| Résumé | (disponible en anglais seulement)
A <5 mm thick volcanic ashfall layer associated with the White River Ash (east lobe [WRAe]) originating from the eruption of Mount Churchill, Alaska (833-850
CE; 1,117-1,100 cal BP) was observed in two freeze cores obtained from Pocket Lake (62.5090ºN, -114.3719ºW), a small subarctic lake located within the city limits of Yellowknife, Northwest Territories, Canada. Here we analyze changes in diatom
assemblages to assess impact of tephra deposition on the aquatic biota of a subarctic lake. In a well-dated core constrained by 8 radiocarbon dates, diatom counts were carried out at 1-mm intervals through an interval spanning 1 cm above and below
the tephra layer with each 1 mm sub-sample represented about 2 years of deposition. Non-metric Multidimensional Scaling (NMDS) and Stratigraphically Constrained Incremental Sum of Squares (CONISS) analyses were carried out and three distinct diatom
assemblages were identified throughout the interval. The lowermost 'Pre-WRAe Assemblage (Pre-WRAeA)' was indicative of slightly acidic and eutrophic lacustrine conditions. Winter deposition of the tephra layer drove a subsequent diatom flora shift to
the 'WRAe Assemblage (WRAeA)' the following spring. The WRAeA contained elevated abundances of taxa associated with oligotrophic, nutrient depleted and slightly more alkaline lake waters. These changes were only apparent in samples within the WRAe
containing interval indicating that they were short lived and only sustained for a single year of deposition. Immediately above the WRAe horizon, a third, 'Post-WRAe Assemblage (Post-WRAeA)' was observed. This assemblage was initially similar to that
of the Pre-WRAeA but gradually became more distinct upwards, likely due to climatic patterns independent of the WRAe event. These results suggest that lacustrine environments are sensitive to perturbations such as deposition of ash fall, but that
ecological communities in subarctic systems can also have high resilience and can recover rapidly. If subsampling of the freeze cores was carried out at a more standard resolution (0.5-1 cm) these subtle diatom ecological responses to perturbation
associated with the WRAe depositional event would not have been observed. This research illustrates the importance of high-resolution subsampling when studying the environmental impact of geologically 'near instantaneous' events such as episodic
deposition of ashfalls. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Cette étude examine la réponse des algues lacustres au dépôt d'une couche de cendres associée à une éruption volcanique. L'étude fournit de
nouvelles informations sur les taux de récupération d'algues après perturbation dans un lac subarctique. |
| GEOSCAN ID | 313554 |
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