Sensitivity of alpine stream ecosystems to climate change and human impacts

• 1 Climatic changes and water resource developments alter the relative contribution of the water sources (glacier-melt, snow-melt, rainfall run-off and springflow) to the discharge regime of alpine streams.
• 2 Likely changes in the magnitude and variability of a range of climatic determinants of glacier behaviour, as a result of an enhanced Greenhouse Effect, are shown to have important implications for the future hydrogeomorphological and thermal dynamics of alpine streams.
• 3 Zoobenthic communities typically show deterministic patterns in alpine streams due to the over-riding influence of water temperature and channel stability. These communities could act as indicators of change in the relative contribution of run-off, particularly to alterations of glacier-melt patterns.
• 4 A reduction of glacial meltwater, following diversion for HEP generation, is used as an example to illustrate the sensitivity of the zoobenthic communities to changes in temperature and flow regimes, and geomorphological dynamics.

     

Damselfish as keystone species in reverse: intermediate disturbance and diversity of reef algae

Substrates located within the defended territories of Hawaiian damselfish for 1 year were subjected to intermediate grazing intensity and, as a result, showed greater diversity of algae than substrates either protected within fish-exclusion cages or exposed to intense fish grazing outside territories. Thus, this damselfish enhances local diversity on reefs through "intermediate-disturbance" effects, and is a keystone species that decreases rather than increases overall predation intensity relative to areas where it is absent.     

Small-scale jetlike features in penumbral chromospheres

We observed fine-scale jetlike features, referred to as penumbral microjets, in chromospheres of sunspot penumbrae. The microjets were identified in image sequences of a sunspot taken through a Ca II H-line filter on the Solar Optical Telescope on board the Japanese solar physics satellite Hinode. The microjets' small width of 400 kilometers and short duration of less than 1 minute make them difficult to identify in existing observations. The microjets are possibly caused by magnetic reconnection in the complex magnetic configuration in penumbrae and have the potential to heat the corona above a sunspot.     

The influence of nitrate,water potential and oxygen tension on nitrogen fixation in detached pea roots

Nodulated pea roots were detached from the plant shoots and exposed to different nitrate concentrations, water potentials, and oxygen tensions. The rates of nitrogen fixation in the detached pea roots following these treatments were determined by the acetylene reduction assay. It was found that increasing the nitrate concentration up to 5 mM brought about reduced nitrogen fixing activity, and this occurred independently of the depressing effects of low water potential and low oxygen tension.

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Auszug Mit Knöllchenbakterien behaftete Erbsenwurzeln wurden von den Pflanzen abgetrennt und verschiedenen Nitratkonzentrationen, Wasserpotentialen und Sauerstoff-Tensionen ausgesetzt. Die Mengen an fixiertem N wurden nach den verschiedenen Behandlungen in den abgetrennten Erbsenwurzeln durch den Azetylen-Reduktionstest bestimmt.Vermehrte Nitrat-Konzentration bis zu 5 mM brachte eine reduzierte Aktivität in der N-Fixierung hervor. Dies war unabhängig vom depressiven Effekt des niedrigen Wasserpotentials und der niedrigen Sauerstoff-Tension.