Limnetica 30

Ver índice del número

Assessment of habitat and water quality of the Portuguese Febros River and one of its tributaries

Bio A., Vieira N., Costa M.J. & Valente A.
2011
30
1
103-116
DOI: 
10.23818/limn.30.09

A physical, chemical and biological characterisation of river systems is needed to evaluate their ecological quality and establish restoration programs. Aquatic benthic macroinvertebrates have proven to be among the most reliable and cost-effective assessment tools for water and habitat quality in streams throughout the world. During one year of seasonal surveys, the state of the Febros River and one of its tributaries, Jaca Creek, were evaluated in terms of habitat, physical, chemical and biological water quality, using benthic macroinvertebrates as ecological indicators. These watercourses suffer pollution from agriculture, industry and urban areas. Both watercourses were moderately to severely degraded, showing spatial and temporal variability in macroinvertebrate communities and water quality. The overall poor river conditions were particularly bad in the upper part of Jaca Creek, which is affected by industry. This upriver site showed higher temperatures, conductivity and dissolved solids than all other sites studied. The best conditions were found in the Gaia Biological Park area, where the habitat quality was evaluated to be high and biotic indices indicated excellent and good water quality in the spring and summer, respectively. However, even this site had biological indicator scores denoting severe degradation in autumn and winter. Macroinvertebrate diversity was low, with populations dominated by pollution-tolerant taxa like Chironomids, particularly in the summer and autumn samples. Abundances were mostly higher in the spring and lower in winter. Percentages of Ephemeroptera and Trichoptera (EPT) were low (totalling 31 % on average), and Plecoptera was completely absent in the samples. The EPT percentage and the percentage of Chironomidae were related to temperature and Biochemical Oxygen Demand (BOD). In comparison to earlier studies, the Febros River improved in both habitat and biological quality. The present study should help to identify specific measures necessary to restore habitat and water quality to reference conditions.

Volver