dc.contributor |
Háskóli Íslands |
dc.contributor |
University of Iceland |
dc.contributor.advisor |
Viggó Þór Marteinsson |
dc.contributor.author |
Bergsten, Pauline |
dc.date.accessioned |
2022-09-28T08:53:35Z |
dc.date.available |
2022-09-28T08:53:35Z |
dc.date.issued |
2022-09 |
dc.identifier.uri |
https://hdl.handle.net/20.500.11815/3491 |
dc.description.abstract |
Surtsey is a volcanic island located on the south-east offshore extension of the Icelandic
rift zone. It was formed during successive eruptions from the seafloor in 1963-1967 and
has been officially protected and studied ever since. It represents an exceptional natural
setting for studying colonization and succession of life on land. Also for subsurface
microbial communities associated with newly formed basaltic tuff deposits in a seawater hydrothermal system that is still active and at temperatures approaching the presumed
thermal limit for functional life. During an international drilling operation at Surtsey in
2017, drill core samples at successive depths as well as associated hot fluids and surface
fumes from fumaroles were collected for microbial investigations. This thesis presents the
first and most comprehensive research of the Surtsey subsurface biosphere. Multiple
approaches were combined on the rare and unique samples to increase the knowledge of
microbial communities inhabiting the oceanic subsurface and of the processes that sustain
such life. These included molecular analyses of environmental DNA through 16S rRNA
gene amplicon and metagenome sequencing, isolation and characterization of bacterial
strains and microscopic investigations. Based on the DNA concentration, the microbial cell
numbers present in the drill cores were estimated to range from about 5×104 to 1×106
cells
per gram of sample. The Surtsey subsurface is therefore a low biomass environment,
making the samples extremely sensitive to external contamination. It is nevertheless a
diverse habitat that hosts bacterial and archaeal clades, including extremophiles, that have
been previously detected in other terrestrial and marine environments. Yet, many clades
belonged to unknown lineages. Predictive functional analyses based on taxonomic
identifications revealed that the Surtsey subsurface biosphere is composed of heterotrophic
microorganisms as well as chemoautotrophs involved in the sulfur, nitrogen, and methane
cycles. However, these results could not be strengthened by the functional metagenomic
investigations as they were inconclusive. Numerous enrichment cultures were initiated
using different conditions and media and resulted in nearly 200 isolated bacterial strains,
which included several novel species. One novel thermophilic bacterial species,
Rhodothermus bifroesti, was fully characterized and its genome was sequenced and
compared with those of the two other described Rhodothermus species. Comparative
analyses revealed that 2.15% of the amplicon sequence variants from the 16S rRNA gene
amplicon sequence datasets were represented by cultivated strains using standard methods.
Finally, putative microbial structures adhering to the basaltic tuff were discovered inside
the numerous interconnected vesicles found in the basaltic glass. All of the findings point
to an active microbial colonization of the Surtsey deposits within 50 years after the
eruptions ended, with possible sources of colonization coming from the surrounding
ecosystems via microbial dissemination and possible adaptations. The thesis establishes a
foundation for future research on the microbial communities that inhabit the Surtsey
subsurface and their temporal succession in the face of a cooling and changing
hydrothermal environment. |
dc.language.iso |
en |
dc.publisher |
University of Iceland, School of Engineering and Natural Sciences, Faculty of Life and Environmental Sciences |
dc.rights |
info:eu-repo/semantics/openAccess |
dc.subject |
Örverur |
dc.subject |
Basalt |
dc.subject |
Eldstöðvar |
dc.subject |
Surtsey |
dc.subject |
Doktorsritgerðir |
dc.title |
Exploration of the Microbial Communities within the Basaltic Subsurface of the Volcanic Island Surtsey in Iceland |
dc.title.alternative |
Rannsókn á neðanjarðar örversamfélögum í basalti á eldfjallaeyjunni Surtsey við Ísland |
dc.type |
info:eu-repo/semantics/doctoralThesis |
dc.contributor.department |
Líf- og umhverfisvísindadeild (HÍ) |
dc.contributor.department |
Faculty of Life and Environmental Sciences (UI) |
dc.contributor.school |
Verkfræði- og náttúruvísindasvið (HÍ) |
dc.contributor.school |
School of Engineering and Natural Sciences (UI) |