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ABSTRACT: Es gibt tatsächlich noch unbekannte Lebensräume. Teils, weil sie unzugänglich sind, teils, weil man sie für eine Besiedelung als absolut ungeeignet empfand und deshalb ignorierte. Die Entdeckung, daß die meterdicke Winterdecke von Hochgebirgsseen der Alpen durch die Anreicherung von Mikroorganismen manchmal einen aktiveren Lebensraum darstellt als die Wassersäule darunter, erregte demgemäß einiges Aufsehen.
Biologie in unserer Zeit 04/2005; 26(6):351 - 355.
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ABSTRACT: Documentary and sediment records (diatoms, chrysophyte stomatocysts, plant pigments, carbon and nitrogen, metals and min-eral magnetics) were used to reconstruct environmental changes in the high alpine lake Gossenköllesee (Tyrol, Austria) during the last 800 years. The records revealed complex interactions between human impact and climate. Gossenköllesee was predominantly influenced by land-use, which supplied nutrients to the lake. Documentary records report intensive sheep and cattle farming in the area around Gossenköllesee during medieval times. Pigments and chrysophyte stomatocysts indicated high nutrient concentrations prior to ca 1770 AD. First changes in land-use, however, were already detected ca 1670 AD. In 1675 AD the "Schwaighof" near Gossenköllesee, a perennial high altitude settlement, was sold to the Earl of Spaur, and farm management probably changed. After approx. 1770 AD in-lake production was reduced, indicating a decrease in land-use. According to historical records, the perennial settlement near Gossenköllesee was abandoned by at least 1890 AD. Gossenköllesee was also affected by fish stocking. Arctic charr (Salmo trutta morpha fario L.) was introduced into the lake, most probably at the end of the 15 th century. A decline in carbon, nitro-gen and the pigments alloxanthin (cryptophytes) and astaxanthin (grazers) indicate a significant removal of grazers by fish. Super-imposed on human activity, climate changes have also had a significant impact on Gossenköllesee. High productivity during the 12 th century suggested by the plant pigment records might have been favoured by temperature increases, indicated by pronounced glacier retreats which began during the 10 th /11 th century. The "Schwaighof" near Gossenköllesee was sold to the Earl of Spaur when winter temperatures declined substantially in the 1670s. Changes in C/N ratio, iron, manganese and mineral magnetics indicated increased detrital input from the catchment, starting approx. 1670 AD. Erosion and detrital input into the lake intensified during cold periods (1688 – 1701 AD and 1820 – 1850 AD), as indicated by a high C/N ratio, metals and mineral magnetics.
J. Limnol. 01/2000; 59:43-52.
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ABSTRACT: The abundance, biomass and morphology of the microbial components (picocyanobacteria, heterotrophic bacteria, heterotrophic and autotrophic nanoflagellates, ciliates) of the pelagic food web of Gossenköllesee were investigated over two summer periods. The density of bacteria remained relatively stable not only over time but also in vertical profiles (2.5 -5.5×10 5 cells ml -1). Bacterial bio-mass ranged between 35 to 63 mgC m -2 (5.4 – 15.3 µgC l -1). Small rod shaped bacteria with mean cell volumes of ∼0.05 µm 3 domi-nated numerically but filamentous forms (longer than 10 µm), mainly found in the upper water layers, amounting to more than 65% of the total bacterial biomass, increased the mean cell volume up to 0.27 µm 3 (SD=0.88). Bacterial biomass represented between 48 and 86% of the total microbial biomass (40 -90 mgC m -2), however at 8 m depth the biomass of heterotrophic flagellates (HNF) reached up to 26 mgC m -3 (2,852 cells ml -1). From 0-4 m depth small spherical HNF species with cell volumes <10 µm 3 were domi-nant, whereas in deeper water layers large flagellates with cell volumes >50 µm 3 dominated throughout the sampling period. Ciliate abundance was low in the upper part of the water column. Only Askenasia chlorelligera and Urotricha cf pelagica occurred with numbers of up to 1,500 cells l -1 . At 8 m depth, Balanion planctonicum was the dominant species throughout the study period reaching numbers of up to 16,000 cells l -1 . Ciliate abundance was significantly correlated with chlorophyll-a concentrations (r s =0.55, p <0.01) confirming the algivory of the dominant species. No significant correlation was found between the parameters of chlorophyll-a, bacteria and HNF but the abundance of ciliates was negatively correlated with the length of bacteria (r s = -0.41, p <0.05).
MOuntain LAkes Research Program J. Limnol. 01/1999; 58:117-126.
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ABSTRACT: There is very little information about the activity of microbial communities on the surface of glaciers, though there is an increasing body of evidence to show that they strongly influence the biogeochemistry of these habitats. We measured bacterial abundance and production in cryoconite holes on Arctic, Antarctic and Alpine glaciers in order to estimate the role of heterotrophic bacteria within the carbon budget of glacial ecosystems. Our results demonstrate an active bacterial community on the surface of glaciers with doubling times that vary from a few hours to hundreds of days depending on the glacier and position (water or sediments) within the cryoconite hole. However, bacterial production is only similar to 2-3% of the published literature values of community respiration from similar habitats, indicating that other types of microbes (e.g. eukaryotic organisms) may also play a role in the C cycle of glaciers. We estimate that only up to 7% of the organic C in cryoconite sediments is utilized by the heterotrophic bacterial community annually, suggesting that the surface of glaciers can accumulate organic carbon, and that this C may be important for biogeochemical activity downstream to adjacent ecosystems.
Annals of Glaciology. 51(56):32-40.
