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| Titel |
The N cycle in Earth subsurface. Reactivity of functional genes to anthropogenic CO2 injections. |
| VerfasserIn |
Rosalia Trias, Emmanuelle Gérard, Paul Le Campion, Sigurður R. Gíslason, Edda S. Aradóttir, Helgui A. Alfreðsson, Kiflom G. Mesfin, Sandra Ó. Snæbjörnsdóttir, Bénédicte Ménez |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095542
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| Publikation (Nr.) |
 EGU/EGU2014-11901.pdf |
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| Zusammenfassung |
| The Nitrogen cycle has been widely studied in surface ecosystems, due to the importance of
this nutrient for the organisms’ development, and to the impact in the environment of
most of the N forms, many of them being considered pollutants. However, little is
known about the importance of the N-related metabolisms in subsurface systems
now recognized to host diverse and active microbial life. In this study, we have
periodically sampled the subsurface aquifers of the Icelandic pilot site for CO2
storage associated with the geothermal plant of Hellisheidi (operated by Reykjavik
Energy; http://www.or.is/en/projects/carbfix). With the aim of understanding the
dynamics of N-cycle in the subsurface, and its reactivity to CO2 injections, we
quantified through qPCR the functional genes amoA (archaea), amoA (bacteria), nirK,
nirS, nosZ, nifH, and the 16SrRNA genes of the anammox, total archaea and total
bacteria.
The 16SrRNA gene quantification provided values of around 107 gene copies/l at non
injection periods. CO2 injection caused first a slight decrease probably due to pH decrease or
toxicity by oxygen contamination during the injections. Two months after injection, the copy
numbers increased up to 109 gene copies/l, and slowly returned to pre-injection values. The
archaeal 16S rDNA copy numbers showed a similar reaction, with higher toxicity effects, and
a lower increase afterwards.
Due to the high reactivity of the microbial populations to CO2 injections, all the N cycle
quantifications were related to the total 16S rDNA copies for normalization. Nitrifying genes
(amoA) were mainly represented by the ammonia oxidizing archaea, and were apparently not
affected by CO2 injections. Anammox bacteria were present in a very low percentage, and
the obtained copy numbers tended to decrease after the injection. These results
were surprising due to the autotrophic character of ammonia oxidizers, but could
be explained by a competitive exclusion. On the contrary, N-fixation (nifH) was
stimulated by the injections, doubling their relative abundance in relation to bacteria 16S
rDNA copy numbers, supplying the N requirements of new biomass formed by
autotrophic CO2 fixation. Finally, denitrifying bacteria (nirK, nirS and nosZ) showed a
higher seasonal variation, but were positively stimulated by the CO2 injections. This
process can be autotrophic in some species, using directly the injected CO2 as C
source.
Altogether the results suggest a high response of the N cycle to the CO2 injections, and its
potential contribution to the formation of new biomass and C fixation. We provide evidences
for the importance of the N cycle on the subsurface and its reactivity to CO2 injections,
being therefore important the consideration of this cycle in CO2 storage modelling. |
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