Hidrológiai Közlöny, 2017 (97. évfolyam)
2017 / 3. szám - TRANSNATIONAL EFFORTS - Sandu, Cristina - Dumitrache, Alina - Radu, Emilia - Dobre, Doru - Tudorache, Mädälina - Mihăilescu, Simona: The importance of good ecological status for the successful revival of Danube sturgeon
15 The Importance of Good Ecological Status for the Successful Revival of the Danube Sturgeon Cristina Sandu1, Alina Dumitrache', Emilia Radu1, Doru Dobre1, MädälinaTudorache2 and Simona Mihäilescu1 1 Institute of Biology Bucharest, Dept, of Ecology, Taxonomy and Nature Conservation, Splaiul Independentei, 296, 060031, sect. 6, Bucharest, Romania ( cristina.sandu@ibiol.ro , cristina.sandu@dstf.eu ) 2 University of Bucharest, Faculty of Chemistry, Dept, of Organic Chemistry, Biochemistry and Catalysis, Bdul Regina Elisabeta 4- 12, sect. 3, Bucharest, Romania Abstract The Water Framework Directive (WFD, 2000/60/EC) brought a significant improvement in water management policies due to its integrative approach. For the first time, the hydrographic connectivity of rivers was considered, while the evaluation of the ecological status comprised not only the abiotic characterization of the aquatic environment and its hydromorphological integrity, but also the status of the biological communities. As large rivers know no political borders and flow through different countries, transnational coordination is needed to harmonize the measures at river basin scale; hence, the riparian countries have strengthened their cooperation in elaborating and jointly implementing transboundary River Basin Management Plans in order to achieve the “good ecological status” of the water bodies. Significant steps have been taken in the Danube River Basin (DRB) since the directive entered into force. However, the achievement of the good ecological status of the Danube water bodies still faces several major challenges: (i) the extent of contamination with hazardous substances, especially with emergent pollutants, the impact of which on aquatic communities needs serious investigation, (ii) although WFD requires no further deterioration of the status of water bodies, new infrastructure projects planned across the Danube Basin (melioration of navigation, hydropower dams, water abstraction for agriculture, flood protection measures) will generate new hydromorphological alterations of the aquatic habitats, while their cumulative impact on the ecological status is not assessed, (iii) the climatic models predict additional changes to the aquatic habitats due to increasing temperatures, modified precipitation regime and increased frequency of extreme weather events (iv) the spreading of invasive alien species threatens the indigenous biodiversity, some of the most successful invaders already being present in the Danube countries. All these challenges should be integrated in the evaluation, as they contribute to the overall decline of the freshwater environment status and the consequent decline of its biodiversity: at European level, over one third of freshwater fish species are threatened with extinction. Large predatory fish, such as sturgeons, situated at the top of the trophic pyramid, are sensitive to the ecological status of water bodies: good water quality is essential to ensure an adequate aquatic environment, good hydromorphology is important to ensure the integrity of and access to their habitats, while the good status of the biological communities is essential to provide proper food resources. As such, the status of their populations reflects the ecological status of their environment, being good indicators of the ecosystem health. Therefore, reaching a good ecological status of the Danube water bodies represents an essential step towards the revival of Danube sturgeon populations. Considering the numerous challenges faced by the freshwater ecosystems of the DRB, a stronger enforcement of water and nature directive requirements is needed to foster the achievement of a good ecological status in the DRB by 2027. Key words Water quality, hydromorphology, biological communities, good ecological status, climate change, invasive alien species, River Danube, sturgeons INTRODUCTION With the adoption of the Water Framework Directive, a new era of water management strategies started; first of all, by upscaling the management units from local to regional level and by taking river hydrographic basins into consideration. Moreover, the systemic approach was introduced in the evaluation of ecological status, by taking into account, besides water chemistry, also habitat integrity and aquatic communities. The monitoring parameters defined by WFD include: • chemical characterization: general parameters (temperature, pH, oxygen, salinity), nutrients, specific pollutants, priority substances or other substances discharged in significant quantities into the water bodies • hydromorphological characterization: hydrological regime, water flow (quantity and dynamics), connection to groundwater bodies, river continuity, morphological conditions, river depth and width variation, structure and substrate of the river bed, structure of the riparian zone • quality of the biological communities: aquatic flora, benthic invertebrates, fish community For the first time, the connection of aquatic species with their habitats was taken into account in the assessment of the ecological status, aquatic communities playing a key role in ensuring the ecosystem’s functionality and the provisioning of ecosystem services such as food and drinking water, oxygen production, nutrient recycling, water self-purification, regulation of atmospheric composition, recreational services, etc. The paper offers a brief insight into the connections between the three main components defining the ecological status, additional challenges that should be taken into account when assessing the ecological status, and the key role played by the ecological status for the successful revival of the critically endangered sturgeons, the flagship species of the Danube river basin.
