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Universidade do Porto (2020)

Assessment of the Ecological Status of an Intermittent river : water quality and ecosystem services

Xavier da Silva Bárbara Elisabete

Titre : Assessment of the Ecological Status of an Intermittent river : water quality and ecosystem services

Auteur : Xavier da Silva Bárbara Elisabete

Université de soutenance : Universidade do Porto

Grade : Mestrado em Ecologia e Ambiente 2020

Résumé
Intermittent rivers and streams are aquatic ecosystems that lose hydrological connectivity during drought periods. Anthropogenic pressures, such as changes in land and water use, combined with climate changes, accelerate the spatial and temporal intermittency of these ecosystems, promoting alterations in their ecology and in the services they provide. Ribeira de Silveirinhos, located in the municipalities of Valongo and Gondomar (north of Portugal), was the intermittent watercourse evaluated in the present study. The aim of this study was to assess the ecological status of Ribeira de Silveirinhos, using the metrics described by the WFD. Additionally, land occupation and ecosystem services provided around each sampling site were assessed. To answer the objective of the study, five sampling sites were selected along Ribeira de Silveirinhos. In each site, physical and chemical parameters of the water were measured, and the benthic macroinvertebrates community was characterized. Ecosystem services in the surrounding area and in the aquatic ecosystem were assessed through a photographic survey over 360º of each site. Sampling was done in three different periods, spring of 2019 and 2020 and autumn of 2019. Physical and chemical parameters showed high concentrations of phosphorus in the places further down the stream. The macroinvertebrate community revealed low values of specific abundance and richness, especially during the dry period. By analyzing the results, we found that Ribeira de Silveirinhos is classified between “poor” and “moderate” in terms of ecological status. Ecosystem services revealed a high improvement potential, mainly due to the eucalyptus monoculture in the surrounding area and the deterioration of the riverbanks. Intermittent streams are undervalued, so their protection is in risk. Thus, it is important to consider the specific ecological functioning of these ecosystems and to adjust the planning and management models in order to guarantee ecological quality and conservation processes.

Mots clés  : Intermittent rivers, WFD, ecological status, water quality monitoring, Ribeira de Silveirinhos.

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