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| Titel |
Vertical stratification of bacteria and archaea in sediments of a boreal stratified humic lake |
| VerfasserIn |
Antti J. Rissanen, Promise Mpamah, Sari Peura, Sami Taipale, Christina Biasi, Hannu Nykänen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103812
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| Publikation (Nr.) |
 EGU/EGU2015-3227.pdf |
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| Zusammenfassung |
| Boreal stratified humic lakes, with steep redox gradients in the water column and in
the sediment, are important sources of methane (CH4) to the atmosphere. CH4
flux from these lakes is largely controlled by the balance between CH4-production
(methanogenesis), which takes place in the organic rich sediment and in the deepest water
layers, and CH4-consumption (methanotrophy), which takes place mainly in the
water column. While there is already some published information on the activity,
diversity and community structure of bacteria in the water columns of these lakes, such
information on sediment microbial communities is very scarce. This study aims
to characterize the vertical variation patterns in the diversity and the structure of
microbial communities in sediment of a boreal stratified lake. Particular focus is on
microbes with the potential to contribute to methanogenesis (fermentative bacteria
and methanogenic archaea) and to methanotrophy (methanotrophic bacteria and
archaea).
Two sediment cores (26 cm deep), collected from the deepest point (~6 m) of a small
boreal stratified lake during winter-stratification, were divided into depth sections
of 1 to 2 cm for analyses. Communities were studied from DNA extracted from
sediment samples by next-generation sequencing (Ion Torrent) of polymerase chain
reaction (PCR) - amplified bacterial and archaeal 16S rRNA gene amplicons. The
abundance of methanogenic archaea was also specifically studied by quantitative-PCR of
methyl coenzyme-M reductase gene (mcrA) amplicons. Furthermore, the community
structure and the abundance of bacteria were studied by phospholipid fatty acid (PLFA)
analysis.
Dominant potential fermentative bacteria belonged to families Syntrophaceae,
Clostridiaceae and Peptostreptococcaceae. There were considerable differences in the
vertical distribution among these groups. The relative abundance of Syntrophaceae started to
increase from the sediment surface, peaked at depth layer from 5 to 10 cm (up to 21 % of
bacterial 16S rRNA gene amplicons) and decreased gradually towards deeper layers while the
relative abundances of Clostridiaceae and Peptostreptococcaceae started to increase at deeper
depths, at 5 cm and 10 cm, respectively, both peaking at depth layer from 20 to 26 cm
(Clostridiaceae up to 13 % and Peptostreptococcaceae up to 11 % of bacterial 16S rRNA
amplicons). Methanogenic community was dominated by acetoclastic methanogens (genus
Methanosaeta), which were most abundant at depth layer from sediment surface to 10 cm (up
to 87 % of archaeal 16S rRNA gene amplicons) and decreased drastically until
the depth of 18 cm having quite stable relative abundance from 18 to 26 cm (5 to
11 % of archaeal 16S rRNA gene amplicons). Hydrogenotrophic methanogens
(Methanoregula, Methanolinea, Methanospirillum, Methanocella) (3 to 11 % of archaeal 16S
rRNA gene amplicons) did not show any specific depth patterns. The proportion of
methanotrophic microbes was very low and they consisted almost completely of type II
methanotrophic bacteria (family Methylocystaceae), which had highest relative abundance at
depth layer from 5 to 10 cm (up to 3 % of bacterial 16S rRNA gene amplicons)
and were almost absent below 15 cm. Anaerobic methanotrophic archaea were not
detected. These findings will be discussed with results from PLFA and q-PCR analyses. |
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