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Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake
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 (62.5090°N, −114.3719°W), a small subarctic lake located...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
PeerJ Inc.
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6348948/ https://www.ncbi.nlm.nih.gov/pubmed/30701131 http://dx.doi.org/10.7717/peerj.6269 |
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author | Hutchinson, Scott J. Hamilton, Paul B. Patterson, R. Timothy Galloway, Jennifer M. Nasser, Nawaf A. Spence, Christopher Falck, Hendrik |
author_facet | Hutchinson, Scott J. Hamilton, Paul B. Patterson, R. Timothy Galloway, Jennifer M. Nasser, Nawaf A. Spence, Christopher Falck, Hendrik |
author_sort | Hutchinson, Scott J. |
collection | PubMed |
description | 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 (62.5090°N, −114.3719°W), 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. |
format | Online Article Text |
id | pubmed-6348948 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | PeerJ Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-63489482019-01-30 Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake Hutchinson, Scott J. Hamilton, Paul B. Patterson, R. Timothy Galloway, Jennifer M. Nasser, Nawaf A. Spence, Christopher Falck, Hendrik PeerJ Ecology 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 (62.5090°N, −114.3719°W), 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. PeerJ Inc. 2019-01-25 /pmc/articles/PMC6348948/ /pubmed/30701131 http://dx.doi.org/10.7717/peerj.6269 Text en ©2019 Hutchinson et al. http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited. |
spellingShingle | Ecology Hutchinson, Scott J. Hamilton, Paul B. Patterson, R. Timothy Galloway, Jennifer M. Nasser, Nawaf A. Spence, Christopher Falck, Hendrik Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
title | Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
title_full | Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
title_fullStr | Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
title_full_unstemmed | Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
title_short | Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake |
title_sort | diatom ecological response to deposition of the 833-850 ce white river ash (east lobe) ashfall in a small subarctic canadian lake |
topic | Ecology |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6348948/ https://www.ncbi.nlm.nih.gov/pubmed/30701131 http://dx.doi.org/10.7717/peerj.6269 |
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