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The occurrence, identity, and activity of microbes from the class Actinobacteria was studied in the surface waters of 10 oligo- to mesotrophic mountain lakes located between 913 m and 2,799 m above sea level. Oligonucleotide probes were designed to distinguish between individual lineages within this group by means of fluorescence in situ hybridization(More)
While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological(More)
  • R Sommaruga
  • 2001
Solar ultraviolet radiation (UVR, 290-400 nm) is a crucial environmental factor in alpine lakes because of the natural increase of the UVR flux with elevation and the high water transparency of these ecosystems. The ecological importance of UVR, however, has only recently been recognized. This review, examines the general features of alpine lakes regarding(More)
We studied the effect of solar radiation on the incorporation of [(sup3)H]thymidine ([(sup3)H]TdR) and [(sup14)C]leucine ([(sup14)C]Leu) by bacterioplankton in a high mountain lake and the northern Adriatic Sea. After short-term exposure (3 to 4 h) of natural bacterial assemblages to sunlight just beneath the surface, the rates of incorporation of(More)
We studied the effects of natural sunlight on heterotrophic marine bacterioplankton in short-term experiments. We used a single-cell level approach involving flow cytometry combined with physiological probes and microautoradiography to determine sunlight effects on the activity and integrity of the cells. After 4 h of sunlight exposure, most bacterial cells(More)
We studied zooplankton dynamics in a groundwater-fed, montane lake during four consecutive years and assessed the importance of water residence time for zooplankton dynamics. Crustacean abundance and biomass were significantly correlated with water residence time and temperature, but showed no significant correlation with phytoplankton biovolume. We(More)
In October 2004, plankton samples were collected from six permanent lakes located between 4960 and 5440 m a.s.l. in the Mount Everest region (Nepal) to assess how spatial and local environmental factors affect natural bacterial community composition. Fingerprinting analysis of the bacterial 16S rRNA gene fragment was done by denaturing gradient gel(More)
We assessed the physicochemical properties of the surface microlayer (SML: first 900 μm) and its underlying water (ULW: 0.2-0.5-m depth) and compared the composition and activity of their bacterial communities in six lakes located across an altitude gradient. Activity was assessed at both the community level, by measuring leucine bulk incorporation, and at(More)
Bacterial production in glacial runoff and aquatic habitats along a c. 500 m transect from the ablation area of a Svalbard glacier (Midre Lovénbreen, 79 degrees N, 12 degrees E) down to a series of proglacial lakes in its forefield were assessed. In addition, a series of in situ experiments were conducted to test how different nutrient sources (glacial(More)
In order to avoid environmental threats, organisms may respond by altering behavior or phenotype. Using experiments performed in high-latitude Siberia and in temperate Sweden, we show for the first time that, among freshwater crustacean zooplankton, the defense against threats from ultraviolet radiation (UV) is a system where phenotypic plasticity and(More)