Showing papers by "Roland Psenner published in 2015"

Biodiversity dynamics of chironomid midges in high-altitude lakes of the Alps over the past two millennia

Abstract: Climate change is one of the key drivers of changes in the biodiversity of the planet. There is, however, a general lack of long-term data sets showing trends in taxonomic diversity of aquatic insects in high mountain environments particularly vulnerable to climate change. Using palaeolimnological techniques, we explored the changes in subfossil chironomid assemblages from three remote water bodies in the Eastern Alps, with the main focus on taxonomic turnover over different intervals of the late Holocene. Major changes in the assemblages coincided with shifts between different climate regimes and were mainly associated with the taxonomic shifts indicating the crossing ecological thresholds related to the ice-cover duration in alpine lakes. Patterns of assemblage turnover through the past 2000 years differ between the study sites. Nevertheless, despite site-specific differences in the physical setting and taxonomic composition, the study sites reveal substantial chironomid assemblage turnover (>1.0 SD) since AD 1850. The highest chironomid turnover (0.87 SD) over the last 30 years (AD 1980–2010), more than three times greater (0.26 SD) than in the previous 30 years, is observed in the lake situated at the highest elevation among the study lakes. Applying non-linear structural equation modelling, we found that cold-season (October–May) temperatures and therefore lake ice phenology are among the most important environment variables affecting the chironomid assemblages. The results of this study suggest that further climate warming will increase the risk of ecological alterations in remote Alpine freshwaters, including major shifts in chironomid fauna.

Prokaryotic community structure in deep bedrock aquifers of the Austrian Central Alps

Abstract: The bacterial and archaeal diversity of deep groundwater systems was investigated based on 16S rRNA-SSCP (single strand conformation polymorphism) fingerprints. The study site included five boreholes along the projected Brenner Base Tunnel in the central Alps of Tyrol, Austria. To obtain representative samples, packer-sealed fractures were sampled at specific depths between 105 and 780 m below surface. Sequence analysis of SSCP bands obtained from 13 samples showed that between 29 and 62 % of the phylotypes belonged to a variety of Proteobacteria including representatives of typical freshwater bacteria of the genera Acidovorax, Aquabacterium, and Sphingomonas. Bacteroidetes (especially Flavobacterium), Firmicutes (Acetobacterium), and candidate division OP3-related sequences were observed in the majority of the analysed groundwaters. On average, 14 % of the detected prokaryotic phylotypes were affiliated with Archaea, comprising the phyla Euryarchaeota, Crenarchaeota and Thaumarchaeota. Most of the archaeal sequences showed low similarities to known cultivated species, with exception of two sequences having 98 % similarity to Methanosaeta sp. A considerable number of thaumarchaeal sequences belonged to two groups related to Nitrososphaera and Nitrosopumilus phylotypes. An environmental clustering of the groundwater samples, based on the bacterial and archaeal phylogeny, revealed a clear distribution pattern of the samples (sites and depths) reflecting the hydrochemical characteristics and underlying geologies.