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| Titel |
Phytoplankton community structure in the Lena Delta (Siberia, Russia) in relation to hydrography |
| VerfasserIn |
A. C. Kraberg, E. Druzhkova, B. Heim, M. J. G. Loeder, K. H. Wiltshire |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-13), S.7263-7277 |
| Datensatznummer |
250085413
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| Publikation (Nr.) |
 copernicus.org/bg-10-7263-2013.pdf |
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| Zusammenfassung |
| The Lena Delta in Northern Siberia is one of the largest river deltas in the
world. During peak discharge, after the ice melt in spring, it delivers
between 60–8000 m3 s−1 of water and sediment into the Arctic Ocean. The
Lena Delta and the Laptev Sea coast also constitute a continuous permafrost
region. Ongoing climate change, which is particularly pronounced in the
Arctic, is leading to increased rates of permafrost thaw. This has already
profoundly altered the discharge rates of the Lena River. But the chemistry
of the river waters which are discharged into the coastal Laptev Sea have
also been hypothesized to undergo considerable compositional changes, e.g.
by increasing concentrations of inorganic nutrients such as dissolved organic
carbon (DOC) and methane. These physical and chemical changes will also
affect the composition of the phytoplankton communities. However, before
potential consequences of climate change for coastal arctic phytoplankton
communities can be judged, the inherent status of the diversity and food web
interactions within the delta have to be established. In 2010, as part of
the AWI Lena Delta programme, the phyto- and microzooplankton community in
three river channels of the delta (Trofimov, Bykov and
Olenek) as well as four coastal transects were investigated to capture
the typical river phytoplankton communities and the transitional zone of
brackish/marine conditions. Most CTD profiles from 23 coastal stations
showed very strong stratification. The only exception to this was a small,
shallow and mixed area running from the outflow of Bykov channel in a
northerly direction parallel to the shore. Of the five stations in this area,
three had a salinity of close to zero. Two further stations had salinities
of around 2 and 5 throughout the water column. In the remaining transects, on
the other hand, salinities varied between 5 and 30 with depth. Phytoplankton
counts from the outflow from the Lena were dominated by diatoms
(Aulacoseira species) cyanobacteria (Aphanizomenon, Pseudanabaena)
and chlorophytes. In contrast, in the
stratified stations the plankton was mostly dominated by dinoflagellates,
ciliates and nanoflagellates, with only an insignificant diatom component
from the genera Chaetoceros and Thalassiosira
(brackish as opposed to freshwater species). Ciliate
abundance was significantly coupled with the abundance of total flagellates.
A pronounced partitioning in the phytoplankton community was also
discernible with depth, with a different community composition and abundance
above and below the thermocline in the stratified sites. This work is a
first analysis of the phytoplankton community structure in the region where
Lena River discharge enters the Laptev Sea. |
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