 |
| Titel |
Effect of permafrost thawing on organic carbon and trace element colloidal speciation in the thermokarst lakes of western Siberia |
| VerfasserIn |
O. S. Pokrovsky, L. S. Shirokova, S. N. Kirpotin, S. Audry, J. Viers, B. Dupré |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 3 ; Nr. 8, no. 3 (2011-03-04), S.565-583 |
| Datensatznummer |
250005563
|
| Publikation (Nr.) |
 copernicus.org/bg-8-565-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
To examine the mechanisms of carbon mobilization and biodegradation during
permafrost thawing and to establish a link between organic carbon (OC) and
other chemical and microbiological parameters in forming thermokarst (thaw)
lakes, we studied the biogeochemistry of OC and trace elements (TEs) in a
chronosequence of small lakes that are being formed due to permafrost
thawing in the northern part of western Siberia. Twenty lakes and small
ponds of various sizes and ages were sampled for dissolved and colloidal
organic carbon, metals and culturable heterotrophic bacterial cell number.
We observed a sequence of ecosystems from peat thawing and palsa degradation
due to permafrost subsidence in small ponds to large, km-size lakes that
are subject to drainage to, finally, the khasyrey (drained lake) formation.
There is a systematic evolution of both total dissolved and colloidal
concentration of OC and TEs in the lake water along with the chronosequence
of lake development that may be directly linked to the microbial
mineralization of dissolved organic matter and the liberation of the
inorganic components (Fe, Al, and TEs) from the organo-mineral colloids.
In this chronosequence of lake development, we observed an apparent decrease
in the relative proportion of low molecular weight <1 kDa (1 kDa ~ 1 nm)
OC concentration along with a decrease in the concentration of total
dissolved (<0.45 μm) OC. This decrease was accompanied by an
increase in the small size organic ligands (probably autochthonous
exometabolites produced by the phytoplankton) and a simultaneous decrease in
the proportion of large-size organic (humic) complexes of allochthonous
(soil) origin. This evolution may be due to the activity of heterotrophic
bacterioplankton that use allochthonous organic matter and dissolved
nutrients originating from peat lixiviation. Most insoluble TEs demonstrate
a systematic decrease in concentration during filtration (5 μm, 0.45 μm)
exhibiting a similar pattern among different samples. At the same
time, there is an increase in the relative proportion of large size
particles over the <1 kDa fraction for most insoluble elements along the
chronosequence of lake evolution. TEs are likely to be bound to colloidal OC
and coprecipitate with the mineral (Fe, Al) part of the colloids. Upon
progressive consumption of dissolved OC by the heterotrophic bacteria, there
is liberation of Fe, Al, and insoluble TEs in the water column that may be
subjected to coagulation in the form of particles or large-size mineral
colloids. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|