Browsing by Author "Sattler, Birgit"

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Carbon fluxes through bacterial communities on glacier surfaces
(2010-12) Anesio, Alexandre M.; Sattler, Birgit; Foreman, Christine M.; Telling, Jon; Hodson, Andy; Tranter, Martyn; Psenner, Roland
There is very little information about the activity of microbial communities on the surfaceof 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 ~2â€“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.
Geomicrobiology of Blood Falls: An iron-rich saline discharge at terminus of the Taylor Glacier, Antarctica
(2004-09) Mikucki, Jill A.; Foreman, Christine M.; Sattler, Birgit; Lyons, W. Berry; Priscu, John C.
Blood Falls, a saline subglacial discharge from the Taylor Glacier, Antarctica provides an example of the diverse physical and chemical niches available for life in the polar desert of the McMurdo Dry Valleys. Geochemical analysis of Blood Falls outflow resembles concentrated seawater remnant from the Pliocene intrusion of marine waters combined with products of weathering. The result is an iron-rich, salty seep at the terminus of Taylor Glacier, which is subject to episodic releases into permanently ice-covered Lake Bonney. Blood Falls influences the geochemistry of Lake Bonney, and provides organic carbon and viable microbes to the lakesystem. Here we present the first data on the geobiology of Blood Falls and relate it to the evolutionary history of this unique environment. The novel geological evolution of this subglacial environment makes Blood Falls an important site for the study of metabolic strategies in subglacial environments and the impact of subglacial efflux on associated lake ecosystems.
Laser-induced fluorescence emission (LIFE) from Lake Fryxell (Antarctica) cryoconites
(2010-12) Sattler, Birgit; Storrie-Lombardi, Michael C.; Foreman, Christine M.; Tilg, Markus; Psenner, Roland
Laser-induced fluorescence emission (LIFE) images were obtained in situ from a 27 cm longice core at Lake Fryxell, Antarctica. The excitation was accomplished with a simple 532nm green laser pen light, and the fluorescence images were captured with a small compact digital camera. The targets for the experiment were mm-scale cryoconite assemblages found in the ice covers of this perennially frozen Antarctic lake. The fluorescence response originates from photo-pigments in cyanobacteriadominated cryoconite assemblages with phycoerythrin (PE) exhibiting the optimal target cross section. This inexpensive, low-mass, low-energy method avoids manipulation of the in situ habitat and individual target organisms and does not disturb the microbial community or the surrounding ice matrix. We establish the correlation between fluorescence intensity and PE concentration.We show that cryoconite fluorescence response does not appear to decrease with depth in the ice cover, in agreement with similar findings at Lake Untersee, a perennially ice-covered lake in Dronning Maud Land, Antarctica. Optical reflection and refraction events at the air/ice interface can complicate quantitative estimates of total pigment concentrations. Laser targeting of a single mm-scale cryoconite can result in multiple neighboring excitation events secondary to reflection and refraction phenomena in the multiple air/ice interface of the bubbles surrounding the primary target.
Metabolic activity and diversity of cyoconites in the Taylor Valley, Antarctica
(2007-12) Foreman, Christine M.; Sattler, Birgit; Mikucki, Jill A.; Porazinska, D. L.; Priscu, John C.
Metabolic activity and biogeochemical diversity within cryoconites from the Canada,Commonwealth, Howard, and Hughes glaciers in the McMurdo Dry Valleys revealed the presence of a productive microbial refuge in this polar desert ecosystem. Fluorescent in situ hybridization showed a high percentage of Cytophaga-Flavobacteria cells in cryoconite sediments (87.2%), while β-Proteobacterial cells dominated the ice overlying the sediment layer (54.2%). The biomass of bacterial cells in the sediments was also greater (4.82 µgC ml-1) than that in the overlying ice (0.18 mgC ml-1) and was related to bacterial productivity (on the basis of thymidine incorporation), which ranged from 36 ng C l-1 d-1 in the overlying ice to 3329 ng C l-1 d -1 in the sediment-containing layers. Bacteria within both the sediments and overlying ice were able to actively incorporate and respire radio-labeled glucose, as well as 17 other dissolved organic carbon compounds. The cryoconites in the Taylor Valley support an active, diverse assemblage of organisms despite the fact that they may remain sealed from the atmosphere for decades. Given the density of the cryoconites in the dry valleys ( ~4–6% of ablation zone surfaces), flushing of the cryoconites during warm years could provide a vital nutrient and organic carbon source to the surrounding polar desert.
Planetary Protection and Mars Special Regions—A Suggestion for Updating the Definition
(2016-02) Rettberg, Petra; Anesio, Alexandre M.; Baker, Victor R.; Baross, Victor R.; Cady, Sherry L.; Detsis, Emmanouil; Foreman, Christine M.; Hauber, Ernst; Ori, Gian G.; Pearce, David A.; Renno, Nilton O.; Ruvkun, Gary; Sattler, Birgit; Saunders, Mark P.; Smith, David H.; Wagner, Dirk; Westall, Frances
We highlight the role of COSPAR and the scientific community in defining and updating the framework of planetary protection. Specifically, we focus on Mars “Special Regions,” areas where strict planetary protection measures have to be applied before a spacecraft can explore them, given the existence of environmental conditions that may be conducive to terrestrial microbial growth. We outline the history of the concept of Special Regions and inform on recent developments regarding the COSPAR policy, namely, the MEPAG SR-SAG2 review and the Academies and ESF joint committee report on Mars Special Regions. We present some new issues that necessitate the update of the current policy and provide suggestions for new definitions of Special Regions. We conclude with the current major scientific questions that remain unanswered regarding Mars Special Regions. Key Words: Planetary protection—Mars Special Regions—COSPAR policy. Astrobiology 16, 119–125.