Global Change Abstracts The Swiss Contribution - SCNAT

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136 Global Change Abstracts – The Swiss Contribution | Oceans and Fresh Water Systems Caenis horaria or Cloeon dipterum is dependent on the trophic state. Caenis horaria is most closely associated with low levels of TP concentrations, while Cloeon dipterum appears to be less sensitive, and is most frequently found in hypertrophic conditions. A probable consequence of these relations, is that Baetidae are always present when Caenidae are also present. Contrastingly, Baetidae is observed as the only mayflies family present in several ponds. Hydrobiologia, 2008, V597, FEB, pp 125-135. 08.1-261 Inorganic carbon fixation by sulfate-reducing bacteria in the Black Sea water column Neretin L N, Abed R M M, Schippers A, Schubert C J, Kohls K, Kuypers M M M Germany, Switzerland Microbiology , Marine & Freshwater Biology , Geochemistry & Geophysics The Black Sea is the largest anoxic water basin on Earth and its stratified water column comprises an upper oxic, middle suboxic and a lower permanently anoxic, sulfidic zone. The abundance of sulfate- reducing bacteria (SRB) in water samples was determined by quantifying the copy number of the dsrA gene coding for the alpha subunit of the dissimilatory (bi)sulfite reductase using real-time polymerase chain reaction. The dsrA gene was detected throughout the whole suboxic and anoxic zones. The maximum dsrA copy numbers were 5 x 10(2) and 6.3 x 10(2) copies ml(-1) at 95 m in the suboxic and at 150 m in the upper anoxic zone, respectively. The proportion of SRB to total Bacteria was 0.1% in the oxic, 0.8-1.9% in the suboxic and 1.2-4.7% in the anoxic zone. A phylogenetic analysis of 16S rDNA clones showed that most clones from the anoxic zone formed a coherent cluster within the Desulfonema-Desulfosarcina group. A similar depth profile as for dsrA copy numbers was obtained for the concentration of non-isoprenoidal dialkyl glycerol diethers (DGDs), which are most likely SRBspecific lipid biomarkers. Three different DGDs were found to be major components of the total lipid fractions from the anoxic zone. The DGDs were depleted in C-13 relative to the delta C-13 values of dissolved CO 2 (delta C-13(CO 2)) by 14-19 parts per thousand. Their delta C-13 values (delta C-13(DGD(II-III))) co-varied with depth showing the least C-13-depleted values in the top of the sulfidic, anoxic zone and the most C-13-depleted values in the deep anoxic waters at 1500 m. This co-variation provides evidence for CO 2 incorporation by the DGD(II-III)-producing SRB, while the 1:2 relationship between delta C-13(CO 2) and delta C-13(DGD(II-III)) indicates the use of an additional organic carbon source. Environmental Microbiology, 2007, V9, N12, DEC, pp 3019-3024. 08.1-262 Impacts of environmental change on water resources in the Mt. Kenya region Notter B, Macmillan L, Viviroli D, Weingartner R, Liniger H P Switzerland Meteorology & Atmospheric Sciences , Water Resources , Modelling Water resources are becoming increasingly scarce in the Mt. Kenya region. Land use and climate change may pose additional challenges to water management in the future. In order to assess the impacts of environmental change, the NRM3 Streamflow Model, a simple, semi- distributed, grid-based water balance model, is evaluated as a too(for discharge prediction in six meso-scale catchments on the western slopes of Mt. Kenya, and used to analyse the impact of Land use and climate change scenarios on water resources. The calibration and validation results show an acceptable performance of the NRM3 Streamflow Model in simulating discharge. Input data represent the main (imitation. Rainfall patterns in the mountainous catchments are very heterogeneous and difficult to capture with the monitoring network. River water abstractions make up 80-100% of naturalized dry season discharge, but amounts can only be approximately estimated. Under the scenarios of (and use and climate change examined, the total amount as well as the variability of discharge wilt increase: Conversion of the forest area to crop- or grassland wilt increase annual runoff by 11% or 59%, respectively, by mainly increasing flood flows and, under cropland, slightly reducing Low flows. Climate change as projected by the IPCC Task Group on Scenarios for Impact Assessment (IPCC-TCGIA, 1999. Guidelines in the use of data for climate impact and adaptation assessment. Version 1. Prepared by Carter, T.R., Hulme, M.., Lal, M., Intergovernmental Panel on Climate Change, Task Group on Scenarios for Climate Impact Assessment.) will result in an increase of annual runoff by 26%, with a severe increase in flood flows, and a reduction of the lowest flows to about a tenth of the current value. Journal of Hydrology, 2007, V343, N3-4, SEP 20, pp 266-278.
Global Change Abstracts – The Swiss Contribution | Oceans and Fresh Water Systems 08.1-263 Influence of temperature and high acetate concentrations on methanogenensis in lake sediment slurries Nozhevnikova A N, Nekrasova V, Ammann A, Zehnder A J B, Wehrli B, Holliger C Switzerland, Russia Limnology , Microbiology , Geochemistry & Geophysics , Marine & Freshwater Biology Methanogenesis from main methane precursors H-2/CO 2 and acetate was investigated in a temperature range of 2-70 degrees C using sediments from Lake Baldegg, Switzerland. Psychrophilic, psychrotrophic, mesophilic, and thermophilic methanogenic microbial communities were enriched by incubations for 1-3 months of nonamended sediment slurries at 5, 15, 30, and 50 degrees C. Isotope experiments with slurries amended with C-14-labeled bicarbonate and C-14-2-acetate showed that in the psychrophilic community (enriched at 5 degrees C), about 95% of methane originated from acetate, in contrast to the thermophilic community (50 degrees C) where up to 98% of methane was formed from bicarbonate. In the mesophilic community (30 degrees C), acetate was the precursor of about 80% of the methane produced. When the hydrogen-carbon dioxide mixture (H-2/CO 2) was used as a substrate, it was directly converted to methane under thermophilic conditions (70 and 50 degrees C). Under mesophilic conditions (30 degrees C), both pathways, hydrogenotrophic and acetoclastic, were observed. At low temperatures (5 and 15 degrees C), H-2/CO 2 was converted into methane by a twostep process; first acetate was formed, followed by methane production from acetate. When slurries were incubated at high partial pressures of H-2/ CO 2, the high concentrations of acetate produced of more than 20 mM inhibited acetoclastic methanogenesis at a temperature below 15 degrees C. However, slow adaptation of the psychrophilic microbial community to high acetate concentrations was observed. Fems Microbiology Ecology, 2007, V62, N3, DEC, pp 336-344. 08.1-264 Macroinvertebrate assemblages in 25 high alpine ponds of the Swiss National Park (Cirque of Macun) and relation to environmental variables Oertli B, Indermühle N, Angelibert S, Hinden H, Stoll A Switzerland Zoology , Biodiversity , Marine & Freshwater Biology , Ecology 137 High-altitude freshwater ecosystems and their biocoenosis are ideal sentinel systems to detect global change. In particular, pond communities are likely to be highly responsive to climate warming. For this reason, the Swiss National Park has included ponds as part of a long-term monitoring programme of the high-alpine Macun cirque. This cirque covers 3.6 km(2), has a mean altitude of 2,660 m a.s.l., and includes a hydrographic system composed of a stream network and more than 35 temporary and permanent ponds. The first two steps in the programme were to (i) make an inventory of the macroinvertebrates of the waterbodies in the Macun cirque, and (ii) relate the assemblages to local or regional environmental variables. Sampling was conducted in 25 ponds between 2002 and 2004. The number of taxa characterising the region (Macun cirque) was low, represented by 47 lentic taxa. None of them was endemic to the Alps, although several species were cold stenothermal. Average pond richness was low (11.3 taxa). Assemblages were dominated by Chironomidae (Diptera), and Coleoptera and Oligochaeta were also relatively well represented. Other groups, which are frequent in lowland ponds, had particularly poor species richness (Trichoptera, Heteroptera) or were absent (Gastropoda, Odonata, Ephemeroptera). Macroinvertebrate assemblages (composition, richness) were only weakly influenced by local environmental variables. The main structuring processes were those operating at regional level and, namely, the connectivity between ponds, i.e. the presence of a physical connection (tributary) and/or small geographical distance between ponds. The results suggest that during the long-term monitoring of the Macun ponds (started in 2005), two kinds of change will affect macroinvertebrate assemblages. The first change is related to the natural dynamics, with high local- scale turnover, involving the metapopulations characterising the Macun cirque. The second change is related to global warming, leading to higher local and regional richness through an increase in the number of colonisation events resulting from the upward shift of geographical ranges of species. At the same time the cold stenothermal species from Macun will be subject to extinction. Hydrobiologia, 2008, V597, FEB, pp 29-41. 08.1-265 Aquatic macroinvertebrate response along a gradient of lateral connectivity in river floodplain channels Paillex A, Castella E, Carron G Switzerland Marine & Freshwater Biology, Ecology, Biodiversity, Zoology
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