affected soils soils of the of the Lena Delta, Siberia Lena Delta, Siberia

(1)

Biodiversity

Biodiversity of of methanogenic methanogenic Archaea Archaea in in permafrost permafrost affected

affected soils soils of the of the Lena Delta, Siberia Lena Delta, Siberia

Lars

Lars Ganzert Ganzert and Dirk Wagner and Dirk Wagner

References

Høj et al. (2005) Archaeal communities in High Arctic wetlands at Spitsbergen, Norway (78°N) as characterized by 16S rRNA gene fingerprinting. FEMS Microbiology Ecology 53, 89-101

Alfred-Wegener-Institute for Polar and Marine Research Forschungsstelle Potsdam Telegrafenberg A 43 14473 Potsdam, Germany lganzert@awi-potsdam.de

Introduction

Hydromorphic arctic tundra soils are an important source of the greenhouse gas methane (CH ₄ ). In these environments carbon is accumulated due to reduced decomposition of organic matter. Most of the climate models predict a global warming for the next century which will lead in deeper and longer thaw processes in the active layer of arctic permafrost soils. Consequently a higher emission of methane and carbon dioxide could be expected. The release of CH 4 is a result of strictly anaerobic methanogenic archaea that use simple compounds (e.g. H 2 , CO 2 , acetate) formed by bacteria during the anaerobic degradation of organic material. There were only a few investigations about the methanogenic community existing in cold terrestrial habitats (e.g. Høj et al., 2005). Here we investigated the methanogenic community structure from three different arctic tundra soils located in the Laptev Sea coast region (Siberia).

Investigation Area

Results

Independent from the chosen temperature or the added substrate the methane production rate reached its maximum in nearly all soil profiles in the upper soil layers. With rising temperature and/or the adding of substrate the methane production rate increase. In all soils we found sequences of Methanomicrobiales and Methanosarcina but no members of Methanobacteriales. In two of the soils we also found sequences belonging to the group of Methanosaetaceae.

Conclusions

In all three investigated permafrost soils methanogens could be detected by activity tests and molecular methods. Sequences of Methanosaetaceae indicating the presence of methanogens that use acetate as the only carbon and energy source. Most of the described Methanomicrobiales use mainly H ₂ /CO ₂ or formate for methanogenesis and growth while the genus Methanosarcina can use a wide variety of substrates. With increasing depth the decrease of DNA bands in DGGE

patterns could be explained by the decrease of temperature and/or the availibility of substrate. Those bands could represent psychrotolerant or psychrophilic methanogenic archaea that are well adapted to these low temperature conditions near the permafrost table. This is supported by the results of the activity tests that show a distinct CH 4 production at a temperature of 5°C.

55 50 45 40 35 30 25 20 15 10 5 0

0,0 0,5 1,0 1,5

CH

4

[nmol h

^-1

g

^-1

]

Depth [cm]

5°C

w.o. substrate H2/CO2 MeOH

55 50 45 40 35 30 25 20 15 10 5 0

0 10 20 30 40 50 60

CH

4

[nmol h

^-1

g

^-1

]

Depth [cm]

18°C

1 2 3 4 5 6 7 8 9 10 11 12

0-5 cm 5-9 cm

9-18 cm 20-35

cm 35-40 cm

40-52 cm 52-56

cm

LD02 6941a LD02 6942a LD02 6943a LD02 6944a

LD02 6945a LD02 6946a

LD02 6946b LD02 6947a

LD02 6947b LD02 6947c

Floodplain (Samoylov Island) Mcb Msbl Msbr Mgm Mgf

Vertical profiles of CH 4 production rates of a Typic Aquortel (floodplain) located on Samoylov Island in dependence of temperature and substrates

DGGE band patterns obtained from soil samples of a Typic Aquortel (floodplain) using a specific primer set (357F-0691R)

45 40 35 30 25 20 15 10 5 0

0 1 2 3 4 5 6

CH

4

[nmol h

^-1

g

^-1

]

Depth [cm]

5°C

45 40 35 30 25 20 15 10 5 0

0 5 10 15 20 25 30

CH

4

[nmol h

^-1

g

^-1

]

Depth [cm]

18°C

Polygon Center (Samoylov Island)

enrichment from 5-10 cm

0-5 cm 5-10

cm 10-15 cm 15-20

cm 20-23 cm 23-30

cm 30-35 cm 35-40

cm 40-45 cm

MeOH Formate

0,2 mM 2 mM 20 mM 0,2 mM 2 mM 20 mM

LD02

6968a

LD02 6969a

LD02 6969b LD02 6970a LD02 6971a

LD02 6971b LD02 6972a LD02 6972b

LD02 6972c LD02 6972d LD02 6973a

LD02 6973b LD02

6974a LD02 6975a

LD02 6976a

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Vertical profiles of CH 4 production rates of a Typic Historthel (polygon centre) located on Samoylov Island in dependence of temperature and substrates

DGGE band patterns obtained from soil samples of a Typic Historthel (polygon centre) using a specific primer set (357F-0691R)

45 40 35 30 25 20 15 10 5 0

0 10 20 30 60 80 100

CH

4

[nmol h

^-1

g

^-1

]

Depth [cm]

5°C

45 40 35 30 25 20 15 10 5 0

0 10 20 30 100 150 200 250 300

CH

4

[nmol h

^-1

g

^-1

]

Depth [cm]

18°C

1 2 3 4 5 6 7 8 9 10 11 12

Polygon Center (Mamontovy Klyk)

0-6 cm 6-12

cm 12-17 cm 17-22

cm 22-29 cm 29-36

cm 36-44 cm

Mcb Msbl Msbr Mgm Mgf

MAK 221a

MAK 221b MAK 222a

MAK 223a MAK 224a

MAK 224b MAK 225a

MAK

225b MAK

226a MAK 227a

Vertical profiles of CH 4 production rates of a Typic Aquiturbel (polygon centre) located at Cape Mamontovy Klyk in dependence of temperature and substrates

DGGE band patterns obtained from soil samples of a Typic Aquiturbel(polygon centre) using a specific primer set (357F-0691R)

Phylogenetic relationships of 16S rDNA sequences retrieved by DGGE from three arctic tundra soils. The sequences obtained in this study are coloured. FP – Floodplain Samoylov Island, PC - Polygon Centre Samoylov Island, MAK – Polygon Centre Cape Mamontovy Klyk. The scale bar represents 0.1 changes per nucleotide.