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| Titel |
Effect of nitrogen fertilization on the activity and diversity of methane oxidising bacteria in the littoral zone of a boreal lake |
| VerfasserIn |
A. Saari, H. M. P. Siljanen, S. Hämäläinen, L. Bodrossy, P. J. Martikainen |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029874
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| Zusammenfassung |
| Freshwater lakes are generally net sources of CH4 and in boreal lakes a major part of the CH4
emissions originates from the littoral zone during the ice-free season. Aerobic CH4 oxidising
bacteria, methanotrophs, significantly limit the flux of CH4 to the atmosphere from
sediments. Increased N load causes eutrophication and subsequent anoxia, which
probably enhances CH4 production. In addition, inorganic nitrogen (ammonium and
nitrate) can inhibit CH4 oxidation. Our study belongs to the research consortium
METHECO (Eurodiversity programme of European Science Foundation), where the
activity and diversity of methane oxidising bacteria are studied in various European
ecosystems.
We studied with in situ manipulation the effects of eutrophication (added nitrogen) on the
activity and diversity of methanotrophs in a littoral wetland of a small and shallow
hyper-eutrophic lake in east-central Finland. We established in the area growing sedges (7-10
m from the shore line) three sampling plots (1.2 m x 1.2 m), which were irrigated four times
(from 4th July to 9th August) with ammonium nitrate solution giving 10 g N m-2for the total
additional nitrogen load during the growing season. Three control plots were irrigated with
equivalent amount of distilled water. The amount of added ammonium nitrate solution or
water did not exceed 10% of the long-term (30 years) average rainfall in the area
during the growing season. Sediment samples were taken from the depths of 0-2 cm,
2-10cm, 10-20 cm and 20-30 cm before, during and after the N treatment. Methane
oxidation potential was studied in 550-ml flasks with sediment slurries and initial
headspace CH4 concentration of 0.1%. The diversity of methanotrophs was studied with
pmoA-microarray.
Methane oxidation was most active in the organic surface sediment layer of 0-10 cm and
the activity decreased with depth. Nitrogen addition in situ did not affect significantly the
potential CH4 oxidation rates, although nitrate inhibited CH4 oxidation in a separate
laboratory experiment. There were differences in the diversity of methanotrophs between
various soil layers. Methanotroph community structure and especially the functional diversity
of methanotrophs showed some changes as a result of the nitrogen fertilization. |
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