Lake ecosystem responses to large volcanic eruptions in recent centuries: diatom and geochemical evidence from varved sediments
(2024) 98.- Abstract
- Volcanic eruptions are documented throughout geological history and are frequently observed and experienced in the modern
world. Strong eruptions in recent decades have resulted in air and water pollution, acid snowfall, disruption in aerial transport and various
illnesses in humans and livestock. Despite their consequences, these recent events are incomparable to eruptions of a much larger
magnitude in recent centuries such as the Icelandic eruption of Laki (1783-84) and Tambora (1815) which are infamously known for
massive losses in livestock and crop failure, resulting in famine and large losses of human life. While their impacts on society and
agriculture are well documented and studied, little is known about how... (More) - Volcanic eruptions are documented throughout geological history and are frequently observed and experienced in the modern
world. Strong eruptions in recent decades have resulted in air and water pollution, acid snowfall, disruption in aerial transport and various
illnesses in humans and livestock. Despite their consequences, these recent events are incomparable to eruptions of a much larger
magnitude in recent centuries such as the Icelandic eruption of Laki (1783-84) and Tambora (1815) which are infamously known for
massive losses in livestock and crop failure, resulting in famine and large losses of human life. While their impacts on society and
agriculture are well documented and studied, little is known about how these major events impacted distant lake ecosystems.
This Ph.D. project focused on varved sediments from Swedish (Odensjön and Kassjön) and Finnish (Nautajärvi) lakes to investigate
the effects of the eruptions of Laki and Tambora on distal lake ecosystems. Varved sediments are annually layered sediments,
providing precise time control facilitating the investigation of changes in the past. Of particular interest to this project is the responses
of diatoms – photosynthetic algae that often dominate lake biomass. Diatoms are great ecological indicators due to their high sensitivity
to changes in the lake and the surrounding catchment. Small changes in environmental conditions can influence diatom productivity
and community structure and they are widely documented to reflect changes in past environmental conditions. Past acid deposition
and any chemical effects in lake waters can be represented by geochemical signals preserved in the sediments. Combined diatom and
geochemical analysis of varved sediments should form a comprehensive view on whether and how distant volcanic eruptions affected
lake ecosystems. This thesis has the following objectives: 1) assess the biogeochemical impacts of transient acidification and
hydroclimatic perturbations related to these two eruptions, and 2) Investigate the type, duration and severity of impacts on the
diatom community and terrestrial biota, and determine the degree of ecosystem resilience. These objectives were addressed
in three subprojects.
Subproject 1 focused on Lake Odensjön in Southern Sweden. This study documented a new varved sediment record and detailed lake
ecosystem dynamics during the last six centuries with the use of diatom and geochemical analysis. A minor response to Laki eruption
may be reflected in the sediments, in the form of a minor decline in pH inferred by changes in the diatom assemblage. Odensjön
represents the southernmost varved sediment record documented in Fennoscandia to date and although no strong signals of major
volcanic eruptions were recorded, it offers a potential to study effects of environmental forcings on the lake ecosystem over
several hundred years. Subproject 2 focused on Lake Kassjön in Northern Sweden. Although the main objective of this study was to
identify eruptions of Laki and Tambora, we evaluated the potential confounding effects of land-use practices and human impacts in the
catchment between 1644 and 1931. Substantial changes were recorded in the sediments in timing with the eruption of Laki,
exhibited by: 1) a significant change in the diatom assemblage structure, 2) qualitative diatom evidence of complex changes in lakewater
chemistry and nutrient and light availability and 3) enhanced chemical weathering indicated by deviations in the typical
biogeochemical processes. No pronounced changes were observed during the eruption of Tambora. Subproject 3 focused on lake
Nautajärvi in Southern Finland. Based on ultra-high resolution sampling of the varved sediments, we found evidence of ecological
stress following the eruption of Laki, reflected by changes in the diatom assemblage and multiple other biotic indicators. Our records
demonstrate how distal boreal ecosystems may undergo complex and yet poorly understood changes in soil chemistry in response to
acid deposition.
This Ph.D. was an interdisciplinary approach combining geochemical proxies, diatom community dynamics and complex statistical
methods to identify major volcanic eruptions during the past centuries. Annually layered sediments from Fennoscandian lakes recorded
various changes in lake ecosystems in timing with the eruption of Laki, which were most pronounced in Kassjön and
Nautajärvi, highlighting the potential of highly resolved studies of varved lake sediments. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/d43e5dbd-3ee6-4aee-9ccc-5b3c33c4e93b
- author
- Silvester, Ethan LU
- supervisor
-
- Dan Hammarlund LU
- Karl Ljung LU
- Per Persson LU
- opponent
-
- Professor Bennion, Helen, Environmental Change Research Centre, Department of Geography, University College London, UK
- organization
- publishing date
- 2024
- type
- Thesis
- publication status
- published
- subject
- keywords
- diatoms, pH, volcanic eruption, lake acidification, lake catchment, land use
- volume
- 98
- pages
- 141 pages
- publisher
- Lund University, Faculty of Science, Department of Geology, Quaternary Sciences
- defense location
- Pangea (sal 229), Geocentrum II, Sölvegatan 12
- defense date
- 2024-12-18 13:15:00
- ISBN
- 978-91-87847-87-5
- 978-91-87847-86-8
- language
- English
- LU publication?
- yes
- id
- d43e5dbd-3ee6-4aee-9ccc-5b3c33c4e93b
- date added to LUP
- 2024-09-13 19:32:17
- date last changed
- 2025-04-04 14:57:45
@phdthesis{d43e5dbd-3ee6-4aee-9ccc-5b3c33c4e93b,
abstract = {{Volcanic eruptions are documented throughout geological history and are frequently observed and experienced in the modern<br/>world. Strong eruptions in recent decades have resulted in air and water pollution, acid snowfall, disruption in aerial transport and various<br/>illnesses in humans and livestock. Despite their consequences, these recent events are incomparable to eruptions of a much larger<br/>magnitude in recent centuries such as the Icelandic eruption of Laki (1783-84) and Tambora (1815) which are infamously known for<br/>massive losses in livestock and crop failure, resulting in famine and large losses of human life. While their impacts on society and<br/>agriculture are well documented and studied, little is known about how these major events impacted distant lake ecosystems.<br/>This Ph.D. project focused on varved sediments from Swedish (Odensjön and Kassjön) and Finnish (Nautajärvi) lakes to investigate<br/>the effects of the eruptions of Laki and Tambora on distal lake ecosystems. Varved sediments are annually layered sediments,<br/>providing precise time control facilitating the investigation of changes in the past. Of particular interest to this project is the responses<br/>of diatoms – photosynthetic algae that often dominate lake biomass. Diatoms are great ecological indicators due to their high sensitivity<br/>to changes in the lake and the surrounding catchment. Small changes in environmental conditions can influence diatom productivity<br/>and community structure and they are widely documented to reflect changes in past environmental conditions. Past acid deposition<br/>and any chemical effects in lake waters can be represented by geochemical signals preserved in the sediments. Combined diatom and<br/>geochemical analysis of varved sediments should form a comprehensive view on whether and how distant volcanic eruptions affected<br/>lake ecosystems. This thesis has the following objectives: 1) assess the biogeochemical impacts of transient acidification and<br/>hydroclimatic perturbations related to these two eruptions, and 2) Investigate the type, duration and severity of impacts on the<br/>diatom community and terrestrial biota, and determine the degree of ecosystem resilience. These objectives were addressed<br/>in three subprojects.<br/>Subproject 1 focused on Lake Odensjön in Southern Sweden. This study documented a new varved sediment record and detailed lake<br/>ecosystem dynamics during the last six centuries with the use of diatom and geochemical analysis. A minor response to Laki eruption<br/>may be reflected in the sediments, in the form of a minor decline in pH inferred by changes in the diatom assemblage. Odensjön<br/>represents the southernmost varved sediment record documented in Fennoscandia to date and although no strong signals of major<br/>volcanic eruptions were recorded, it offers a potential to study effects of environmental forcings on the lake ecosystem over<br/>several hundred years. Subproject 2 focused on Lake Kassjön in Northern Sweden. Although the main objective of this study was to<br/>identify eruptions of Laki and Tambora, we evaluated the potential confounding effects of land-use practices and human impacts in the<br/>catchment between 1644 and 1931. Substantial changes were recorded in the sediments in timing with the eruption of Laki,<br/>exhibited by: 1) a significant change in the diatom assemblage structure, 2) qualitative diatom evidence of complex changes in lakewater<br/>chemistry and nutrient and light availability and 3) enhanced chemical weathering indicated by deviations in the typical<br/>biogeochemical processes. No pronounced changes were observed during the eruption of Tambora. Subproject 3 focused on lake<br/>Nautajärvi in Southern Finland. Based on ultra-high resolution sampling of the varved sediments, we found evidence of ecological<br/>stress following the eruption of Laki, reflected by changes in the diatom assemblage and multiple other biotic indicators. Our records<br/>demonstrate how distal boreal ecosystems may undergo complex and yet poorly understood changes in soil chemistry in response to<br/>acid deposition.<br/>This Ph.D. was an interdisciplinary approach combining geochemical proxies, diatom community dynamics and complex statistical<br/>methods to identify major volcanic eruptions during the past centuries. Annually layered sediments from Fennoscandian lakes recorded<br/>various changes in lake ecosystems in timing with the eruption of Laki, which were most pronounced in Kassjön and<br/>Nautajärvi, highlighting the potential of highly resolved studies of varved lake sediments.}},
author = {{Silvester, Ethan}},
isbn = {{978-91-87847-87-5}},
keywords = {{diatoms; pH; volcanic eruption; lake acidification; lake catchment; land use}},
language = {{eng}},
publisher = {{Lund University, Faculty of Science, Department of Geology, Quaternary Sciences}},
school = {{Lund University}},
title = {{Lake ecosystem responses to large volcanic eruptions in recent centuries: diatom and geochemical evidence from varved sediments}},
url = {{https://lup.lub.lu.se/search/files/200405834/PhD_Thesis_Ethan_Silvester_-_kappa.pdf}},
volume = {{98}},
year = {{2024}},
}