Alpine glacier-fed turbid lakes are discontinuous cold polymictic rather than dimictic.
Ontology highlight
ABSTRACT:
SUBMITTER: Peter H
PROVIDER: S-EPMC5478930 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Viruses are ubiquitous in aquatic ecosystems where they significantly contribute to microbial mortality. In glacier-fed turbid lakes, however, viruses not only encounter low host abundances, but also a high number of suspended mineral particles introduced by glacier meltwaters. We hypothesized that these particles potentially lead to unspecific adsorption and removal of free virus from the plankton, and thus significantly reduce their abundance in this type of lake. We followed the distribution of free virus-like particles (VLP) during the ice-free season across a turbidity gradient in four alpine lakes including one adjacent clear system where hydrological connectivity to the receding glacier is already lost. In the glacier-fed turbid lakes, VLP abundance increased with distance to the glacier, but the highest numbers were observed in the clear lake by the end of August, coinciding with the maximum in prokaryotic abundance. Our results suggest that viral loss by attachment to particles is less important than expected. Nevertheless, the relatively lower variability in VLP abundance and the lower virus-to-prokaryote ratio found in the turbid lakes than in the clear one point to a rather low temporal turnover and thus, to a reduced impact on microbial communities.
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Project description:Zooplankton, a group of aquatic animals important as trophic link in the food web, are exposed to high levels of UV radiation (UVR) in clear alpine lakes, while in turbid glacier-fed lakes they are more protected. To study the interplay between behavioral and physiological protection responses in zooplankton from those lakes, we sampled six lakes of different UVR transparency and glacial turbidity. Copepods were absent in the upper water layers of the clearest lake, while in glacier-fed lakes they were more evenly distributed in the water column. Across all lakes, the weighted copepod mean depth was strongly related to food resources (chlorophyll a and rotifers), whereas in the fishless lakes, glacial turbidity largely explained the vertical daytime distribution of these organisms. Up to ~11-times (mean 3.5) higher concentrations of photo-protective compounds (mycosporine-like amino acids, MAAs) were found in the copepods from the clear than from the glacier-fed lakes. In contrast to carotenoid concentrations and antioxidant capacities, MAA levels were strongly related to the lake transparency. Copepods from alpine lakes rely on a combination of behavioral and physiological strategies adapted to the change in environmental conditions taking place when lakes shift from glacially turbid to clear conditions, as glacier retreat proceeds.
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Project description:Monitoring of plant succession in glacier forelands has so far been restricted to field sampling. In this study, in situ vegetation sampling along a chronosequence between Little Ice Age (LIA) maximum extent and the recent glacier terminus at Jamtalferner in the Austrian Alps is compared to time series of the Normalized Difference Vegetation Index (NDVI) calculated from 13 Landsat scenes (1985-2016). The glacier terminus positions at 16 dates between the LIA maximum and 2015 were analysed from historical maps, orthophotos and LiDAR images. We sampled plots of different ages since deglaciation, from very recent to approx. 150 years: after 100 years, roughly 80% of the ground is covered by plants and ground cover does not increase significantly thereafter. The number of species increases from 10-20 species on young sites to 40-50 species after 100 years. The NDVI increases with the time of exposure from a mean of 0.11 for 1985-1991 to 0.20 in 2009 and 0.27 in 2016. As the increase in ground cover is clearly reproduced by the NDVI (R² ground cover/NDVI 0.84) - even for sparsely vegetated areas -, we see a great potential of satellite-borne NDVI to perform regional characterizations of glacier forelands for hydrological, ecological and hazard management-related applications.
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