Showing papers by "Roland Psenner published in 2016"

Impacts of Climate Warming on Alpine Lake Biota Over the Past Decade

Abstract: Alpine temperatures have risen at twice the rate compared to the northern-hemispheric average during the past century. This can be expected to affect Alpine lake ecosystems via, for example, intensified thermal stratification, shorter ice cover periods, and altered catchment processes. Our study assesses changes in some main constituents of the planktic and benthic communities of five mid-Alpine lakes in the Niedere Tauern region in Austria in relation to climatic warming, by comparing community and environmental data from 1998–1999 to data from 2010–2011. Although lake chemistry remained relatively stable between the study periods, we observed an increase in lake water temperatures and a decrease in ice cover durations. Several of the dominant diatom species and chrysophyte cyst types show relatively clear changes; the responses of the whole communities, however, are less evident. Yet, in particular, diatoms show distinct assemblage changes along the climatic gradients in the two lakes with the ...

Trade-off between taxon diversity and functional diversity in European lake ecosystems.

Abstract: Inferring ecosystem functioning and ecosystem services through inspections of the species inventory is a major aspect of ecological field studies. Ecosystem functions are often stable despite considerable species turnover. Using metatranscriptome analyses, we analyse a thus-far unparalleled freshwater data set which comprises 21 mainland European freshwater lakes from the Sierra Nevada (Spain) to the Carpathian Mountains (Romania) and from northern Germany to the Apennines (Italy) and covers an altitudinal range from 38 m above sea level (a.s.l) to 3110 m a.s.l. The dominant taxa were Chlorophyta and streptophytic algae, Ciliophora, Bacillariophyta and Chrysophyta. Metatranscriptomics provided insights into differences in community composition and into functional diversity via the relative share of taxa to the overall read abundance of distinct functional genes on the ecosystem level. The dominant metabolic pathways in terms of the fraction of expressed sequences in the cDNA libraries were affiliated with primary metabolism, specifically oxidative phosphorylation, photosynthesis and the TCA cycle. Our analyses indicate that community composition is a good first proxy for the analysis of ecosystem functions. However, differential gene regulation modifies the relative importance of taxa in distinct pathways. Whereas taxon composition varies considerably between lakes, the relative importance of distinct metabolic pathways is much more stable, indicating that ecosystem functioning is buffered against shifts in community composition through a functional redundancy of taxa.

Molecular investigation of protistan diversity along an elevation transect of alpine lakes

Abstract: Ecological gradients are one of the main reasons for changes in biodiversity. However, whether what is known to be true for plants and animals also applies to protists in the same way is largely unknown. Along an alpine elevation gradient, including 29 freshwater lakes, we investigated ecological drivers of protistan diversity and community structure, as well as the explanatory value of the species−area relationship for protistan diversity using a deep-sequencing approach. We found that species richness does not decrease with elevation, nor is elevation a major factor explaining the observed shifts in community composition. The observed protistan communities differ depending on many factors, with pH and nutrient concentrations being most important. Considering distinct subgroups, Chrysophyceae accurately reflect the pattern of the overall protistan community. Within the investigated elevation gradient, species richness was correlated with the area of individual lakes irrespective of their elevation. However, we found no support for decreasing species richness with elevation, as known for plants and animals.