|
Résumé :
|
Freshwater ecosystems are threatened by several pressures worldwide. Water pollution and eutrophication, the degradation and fragmentation of aquatic and riparian environments, overexploitation of resources, the dispersion of non-native species and more recently climate change have contributed to the loss of biodiversity and ecological integrity of rivers. For this reason, river conservation and management are essential to guarantee all associated ecosystem goods and services, this taking into account the biotic and abiotic factors. Which leads to the objectives of the present study which were: 1) to evaluate the impact of abiotic factors on the biological quality of a watercourse, the river Fervença belonging to the drainage bassin of River Sabor (NE of Portugal), subject to anthropic pressures, and 2) to determine the influence of biotic factors, namely the complex relationship between fish and bivalves, in the ecological integrity of lotic systems. In the spring of 2020, abiotic (i.e. water quality and habitats) and biotic (i.e. macroinvertebrates and fish) characterization of 7 sampling sites were made, using the Water Framework Directive protocols. The results showed a marked decrease in the quality of water, habitats and biota in sampling sites located downstream of the city of Bragança, as a result of the input of contaminants from the urban environment, despite the presence of a wastewater treatment plant (WWTP). The degradation of abiotic conditions has led to the disappearance of species sensitive to pollution and to the loss of biodiversity, biotic relationships and ecological functions in the aquatic system. In this context, the relationship between a bivalve, the unionoid Anodonta anatina, and the fish fauna present in the river Sabor was studied. Four native Iberian species (Luciobarbus bocagei, Squalius alburnoides, Squalius carolitertii and Pseudochondrostoma duriense) and one non-native species (Alburnus alburnus) were tested in the laboratory. All fish species functioned as viable hosts for Anodonta anatina due to the wide distribution of this bivalve, although the higher rates of metamorphosis were found for a native species, Squalius carolitertii. For the conservation and management of NE Portugal's aquatic systems, measures for the rehabilitation of disturbed ecosystems and the conservation of priority habitats are essential, namely for threatened native species.
|
