the Expedition ARKTIS-XIX/4 of the research vessel POLARSTERN ...

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Generally, all sampled benthic substrates (surface sediment, rocks, stones,
submerged vegetation) show a relatively high diversity of benthic diatoms compared
to lakes for example in Northwest Greenland (Blake et al. 1992). The seemingly most
abundant diatom genera are Pinnularia, Tabellaria and Navicula (Fig. 6.3-3). Again,
these findings have to be confirmed by detailed taxonomical analyses which will also
reveal differences in the species composition and diversity of diatom communities in
dependence of specific lake water characteristics.
6.4 Measurement of trace gas emissions from soils and lakes
Svenja Kobabe, Nadja Hultzsch
Fig. 6.3-3: Examples of living
benthic diatoms from various
substrats from lakes on Store
Koldewey. A. Chain of Melosira
from the submerged moss
Drepanocladus. B. Pinnularia
sp. (left) and Stauroneis sp.
(right) from a soft sediment
surface. C, D. Long zig-zag
chain of Tabellaria sp. washed
from Drepanocladus.
The exchange of the climate relevant trace gases methane (CH4) and carbon dioxide
(CO2) in northern terrestrial environments has attracted much attention in recent
years. One reason for this is, that about 14% of the global soil carbon are stored in
the soils of arctic and sub arctic regions. These regions constitute a substantial part
of the global natural wetlands and form the largest single source of atmospheric
methane (e.g., Fung et al. 1991, Christensen et al. 1996). Trace gas fluxes have
been studied in some detail in northern temperate/boreal (e.g., Silvola et al. 1996,
Moosavi & Crill 1997), sub arctic (Whalen & Reeburgh 1990, Svensson et al. 1999)
and low arctic systems (Whalen & Reeburgh 1990, Christensen 1993, Wagner et al.
2003), but about the high arctic just a few data exist (Christensen et al. 2000),
probably most because of its inaccessibility. One aim of our study is to receive more
information about trace gas fluxes in this region.
The emitted methane is the result of two main processes: 1.) the production by micro
organisms as the final step in the anaerobic decomposition of organic material. 2.)
The oxidation of methane to CO2 by another group of micro organisms. To