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Abstract(s)
A biodiversidade de rios está ameaçada por um conjunto de pressões que englobam a poluição e eutrofização da água, a sobrepesca e pesca ilegal, a dispersão de espécies invasoras e a fragmentação e degradação de habitats aquáticos e ribeirinhos, potenciadas por um cenário de alterações climáticas. A escassez de água tem levado à multiplicação de infraestruturas hidráulicas de retenção de água, com a construção de grandes e pequenas barragens e uma multitude de pequenas barreiras (açudes) cujos efeitos na biodiversidade não estão totalmente esclarecidos, em especial nas regiões mediterrânicas. Neste enquadramento, o presente estudo teve como objetivo avaliar os efeitos na biodiversidade de dois açudes construídos no rio Maçãs, primordialmente para assegurar o abastecimento público de Vimioso (NE Portugal). Durante a primavera e verão de 5 anos sucessivos (2018 a 2022) foi monitorizada, através de metodologias definidas pela Diretiva-Quadro da Água, a qualidade ecológica em 4 locais de amostragem situados na proximidade de ambos os açudes. Foi ainda testada a transponibilidade das barreiras pelas espécies piscícolas nativas e analisada a ecologia alimentar da espécie piscícola dominante. Os resultados obtidos mostraram que a qualidade da água não diminuiu significativamente nas albufeiras de ambos os açudes, ao contrário da menor qualidade hidromorfológica (homogeneidade de habitats, degradação da galeria ripícola) e de um substancial decréscimo na diversidade de invertebrados e na abundância de espécies piscícolas nativas. Com efeito, os ambientes lênticos aparecem dominados por espécies exóticas de carácter invasor, originárias da América do Norte, caso de 2 crustáceos, o lagostim-sinal e o lagostim-vermelho, e de um peixe de pequenas dimensões, a perca-sol, mas com impactes negativos nos sistemas aquáticos. A ecologia alimentar da espécie revelou uma elevada capacidade de adaptação a condições adversas severas, sugerindo uma tendência para o domínio avassalador na região, caso os fenómenos hidrológicos extremos prossigam, contribuindo para a diminuição ou desaparecimento de espécies endémicas ameaçadas. A gestão das infraestruturas hidráulicas deverá garantir o cumprimento de caudais ecológicos e a permeabilidade das barreiras, através da implementação de passagens de peixes, de modo a permitir a migração dos peixes nativos, fundamental para o gene-flow e para a sua conservação no rio Maçãs.
The biodiversity of rivers is threatened by a set of pressures that include water pollution and eutrophication, overfishing and illegal fishing, the spread of invasive species and the fragmentation and degradation of aquatic and riparian habitats, boosted by a scenario of climate change. Water scarcity has led, over time, to the multiplication of hydraulic infrastructures for water retention purposes, with the construction of large and small dams and a multitude of small barriers (weirs) whose effects on biodiversity are not fully understood, especially in the Mediterranean regions. In this context, the present study aimed to evaluate the effects on biodiversity of two weirs built on the River Maçãs, primarily to ensure the public supply of Vimioso (NE Portugal). During the spring and summer of 5 successive years (2018 to 2022), the ecological quality of 4 sampling sites defined in lotic and lentic environments, located near the reservoirs, was monitored using methodologies defined by the Water Framework Directive. Studies were also carried out to verify the transposability of the barriers by native fish species and at the feeding ecology of the dominant fish species. The results obtained showed that the water quality did not decrease significantly in the reservoirs of the weirs, contrarily to the lower hydromorphological quality registered (homogeneity of habitats, degradation of the riparian gallery) and a substantial decrease in the diversity of invertebrates and in the abundance of native fish species. Indeed, the lentic environments appear to be dominated by invasive alien species, form North America, such as 2 crustaceans, the signal crayfish and the red swamp crayfish, and of a small fish, the pumpkinseed, known by their negative impacts on the aquatic systems where it has been detected. Furthermore, the food ecology of pumpkinseed revealed a high capacity to adapt to severe adverse conditions, suggesting a tendency towards overwhelming dominance in the region if extreme hydrological phenomena persist, contributing to the decline or disappearance of threatened endemic species. The management of hydraulic infrastructures should guarantee compliance with ecological flows and the permeability of the barriers, through the implementation of fish passages, to allow the migration of native cyprinids and leuciscids, fundamental for the gene-flow and for its conservation in the River Maçãs.
The biodiversity of rivers is threatened by a set of pressures that include water pollution and eutrophication, overfishing and illegal fishing, the spread of invasive species and the fragmentation and degradation of aquatic and riparian habitats, boosted by a scenario of climate change. Water scarcity has led, over time, to the multiplication of hydraulic infrastructures for water retention purposes, with the construction of large and small dams and a multitude of small barriers (weirs) whose effects on biodiversity are not fully understood, especially in the Mediterranean regions. In this context, the present study aimed to evaluate the effects on biodiversity of two weirs built on the River Maçãs, primarily to ensure the public supply of Vimioso (NE Portugal). During the spring and summer of 5 successive years (2018 to 2022), the ecological quality of 4 sampling sites defined in lotic and lentic environments, located near the reservoirs, was monitored using methodologies defined by the Water Framework Directive. Studies were also carried out to verify the transposability of the barriers by native fish species and at the feeding ecology of the dominant fish species. The results obtained showed that the water quality did not decrease significantly in the reservoirs of the weirs, contrarily to the lower hydromorphological quality registered (homogeneity of habitats, degradation of the riparian gallery) and a substantial decrease in the diversity of invertebrates and in the abundance of native fish species. Indeed, the lentic environments appear to be dominated by invasive alien species, form North America, such as 2 crustaceans, the signal crayfish and the red swamp crayfish, and of a small fish, the pumpkinseed, known by their negative impacts on the aquatic systems where it has been detected. Furthermore, the food ecology of pumpkinseed revealed a high capacity to adapt to severe adverse conditions, suggesting a tendency towards overwhelming dominance in the region if extreme hydrological phenomena persist, contributing to the decline or disappearance of threatened endemic species. The management of hydraulic infrastructures should guarantee compliance with ecological flows and the permeability of the barriers, through the implementation of fish passages, to allow the migration of native cyprinids and leuciscids, fundamental for the gene-flow and for its conservation in the River Maçãs.
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Keywords
Barreiras Rios Integridade ecológica Impactes Gestão Rio Maçãs