Impacts du changement climatique sur la gestion multi-objectif de réservoirs : cas d'étude sur le bassin versant de la Seine, France

International audienceAdaptation strategies will be needed to cope with the hydrological consequences of projected climate change. In this perspective, the management of many artificial reservoirs will have to be adapted to continue to fulfil downstream objectives (e.g. flow regulation). This study evaluates the sustainability of the management rules of the artificial reservoirs on the Seine River basin, France, under climate change scenarios. The Seine River basin at Paris (43,800 km2) has major socio-economic stakes for France, and the consequences of droughts and floods may be dramatic. In this context, four large multi-purpose reservoirs were built on the basin during the twentieth century for low-flow augmentation and flood alleviation. A hydrological modelling chain was designed to explicitly account for reservoir management rules. It was calibrated in current conditions and then fed by the outputs of seven climate models in present and future conditions, forced by the A1B IPCC scenario, downscaled using a weather-type method and statistically bias-corrected. The results show that the hydrological model performs quite well in current conditions. The simulations made in present and future conditions indicate a decrease in water availability and summer low flows, but no significant trends in high flows. Simulations also indicate that there is room for progress in the current multi-purpose management of reservoirs and that it would be useful to define proper adaptation strategies

Association of a Nonmuscle Myosin II with Axoplasmic Organelles

Association of motor proteins with organelles is required for the motors to mediate transport. Because axoplasmic organelles move on actin filaments, they must have associated actin-based motors, most likely members of the myosin superfamily. To gain a better understanding of the roles of myosins in the axon we used the giant axon of the squid, a powerful model for studies of axonal physiology. First, a ∼220 kDa protein was purified from squid optic lobe, using a biochemical protocol designed to isolate myosins. Peptide sequence analysis, followed by cloning and sequencing of the full-length cDNA, identified this ∼220 kDa protein as a nonmuscle myosin II. This myosin is also present in axoplasm, as determined by two independent criteria. First, RT-PCR using sequence-specific primers detected the transcript in the stellate ganglion, which contains the cell bodies that give rise to the giant axon. Second, Western blot analysis using nonmuscle myosin II isotype-specific antibodies detected a single ∼220 kDa band in axoplasm. Axoplasm was fractionated through a four-step sucrose gradient after 0.6 M KI treatment, which separates organelles from cytoskeletal components. Of the total nonmuscle myosin II in axoplasm, 43.2% copurified with organelles in the 15% sucrose fraction, while the remainder (56.8%) was soluble and found in the supernatant. This myosin decorates the cytoplasmic surface of 21% of the axoplasmic organelles, as demonstrated by immunogold electron-microscopy. Thus, nonmuscle myosin II is synthesized in the cell bodies of the giant axon, is present in the axon, and is associated with isolated axoplasmic organelles. Therefore, in addition to myosin V, this myosin is likely to be an axoplasmic organelle motor