River regulation, urban development and the construction of a hydroelectric power plant have considerably changed the ecological condition of the Danube section in Vienna. In 1997, the previously straight shoreline of the Danube in this area was reconstructed by creating shallow water areas, coves, gravel banks and side channels. These inshore structures were created to increase habitat diversity in this area and to establish, together with existing ponds, a system of stepping stone biotopes, which serve as migration linkage through the municipal area of Vienna. A monitoring programme (1998-2001) was established to assess the functional integrity of these structures. A multi-species-approach using odonates, amphibians, and fish was developed to cover aquatic, amphibious and terrestrial habitat components. As demonstrated in this study, rehabilitation of heavily altered systems may play an important role in improving ecologically degraded areas and in reconnecting isolated landscape patches. A new metric (Floodplain Index) was applied for defining an ecological management objective, for characterizing the newly created structures and for assessing habitat heterogeneity.

Over the last 125 years, river regulation has considerably changed the ecological conditions of the Austrian Danube and its floodplains such that the system is now very fragmented. Within the municipal area of Vienna, these changes have been particularly severe: river embankments and a bypass channel (the 'New Danube'), separated from the main river by an artificial island ('Danube Island'), are the key elements of flood control, and river levels are controlled by the Vienna hydroelectric power plant ('Freudenau'). During construction of the hydroelectric power plant, the previously straight shoreline of the 21-km long Danube island, with its steep embankments, was restructured by creating shallow water areas, gravel banks, small permanent backwaters and temporary waters. This paper describes the scheme and the results from the first year of a 4-year monitoring programme ('Danube Island Monitoring Programme', DIMP) investigating the colonization and successional processes of these areas by monitoring relevant indicator groups (vegetation, dragonflies, amphibians, reptiles, waterfowl). Copyright (C) 2000 John Wiley & Sons, Ltd.

In preliminary investigations the influence of orally administered dimethyl mercury on the motor coordination of rats was tested. An ED50 = 65.9±1.7 mg Hg/kg for standard equilibration test of the motor coordination has been found.

Investigations on the distribution and the excretion of mercury in rats after oral intake of dimethyl mercury have been performed. The findings are compared with the results obtained with monomethyl mercury by other authors. Besides a very high concentration of mercury in the blood of the treated animals the greatest accumulation of mercury in hair as well in the kidney, the spleen and the liver has been found. Much less mercury has been detected in samples of CNS. However, observations during a period of 21 days indicate that in samples of CNS the decline of Hg is less rapid than in other tissues. The excretion of mercury by urine and faeces are of the same order of magnitude as in the case of monomethyl mercury.