Ana Ostojić

The Danube River Basin

The Danube is the European river par excellence; a river that most effectively defines and integrates Europe. It links more countries than any other river in the world. The Danube River Basin (DRB) collects waters from the territories of 19 nations and it forms the international boundaries for eight of these. The rivers largely eastward course has served as a corridor for both migration and trade and a boundary strongly guarded for thousands of years. This chapter provides an overview of the DRB, including the three main sections: upper, middle, and lower Danube, the delta and 11 major tributaries. Culturally and biologically, the river has always been a separator as well as a connector. It served as a migration corridor for organisms and cultures and has been an area of dispute as well as a major melting pot of cultures. It is also listed as one of the worlds top 10 rivers at risk. The development of the Trans-European Network for Transport, the ongoing construction of small- and medium-sized hydropower plants along its tributaries, bed incision, truncation of sediment transport, and rapid land-use change within the basin pose major threats.

Response of aquatic protists to electric field exposure

Abstract Purpose: To test the effects of short-term exposure of aquatic organisms to electric field (EF) with negligible magnetic component. Materials and methods: We built a plate capacitor that served as a source of EF of strengths that can be found in nature near transmission lines. We exposed two cultured protist species Euglena viridis and Paramecium caudatum to EFs for 24 hours and monitored their abundance, morphology, intracellular superoxide anion (by dihydroethidium [DHE]), hydrogen peroxide by (H2DCF) and lipid peroxidation (MDA) contents, catalase (CAT) and superoxide dismutase (SOD) activity. Results: We found that even short-term exposure to low strength EF causes changes in population abundance, morphology and oxidative stress response in both species. As the EF strength increased, abundance of both species decreased. However, at weaker EFs, fission rates were seemingly promoted. We noted a decrease in size in both organisms in directions perpendicular to their fission planes correlated with EF strength. DHE and H2DCF fluorescence intensity and SOD activity were higher in organisms exposed to the stronger EFs. Conclusions: We suggest that the electric component of the field, rather than the magnetic, is the main cause of all the noted effects. As a result, aquatic organisms should be given greater importance in studies assessing the effects of EMFs in spite of the attenuating effects of water to EF strengths.