Aquatic biodiversity and quality of streams in certified eucalypt plantations in Central Portugal.
In Portugal, more than 150.000 ha of eucalypt plantations are managed in compliance with international certification systems. The objective of this work was to evaluate the biodiversity and the ecological quality of streams associated with certified eucalypt plantations, using different aquatic communities as biological quality indicators - fish, amphibians, and macroinvertebrates - and a morphological quality index (condition of river bed and banks). This study was carried out in two streams located in the central region of Portugal, the Foz stream (medium size and permanent flow regime) and the Rouxinóis stream (small size and intermittent flow regime), surrounded by certified eucalyptus plantations and, consequently, presenting protected riparian buffer zones. The Foz stream revealed fish assemblages with a high species richness that, although dominated by an exotic taxon (Gobio lozanoi), included several endangered species. However, the amphibian fauna was not very abundant, probably due to the great diversity and density of fish and the strong presence of the red swamp crayfish (Procambarus clarkii). A good morphological condition was also found for this stream, as well as a high diversity of the macroinvertebrate community, reflecting good water quality. In the Rouxinóis stream the fish community was close to the potential for this river type and the amphibian fauna was diverse and abundant. However, a poor macroinvertebrate community was observed, most likely due to the lower habitat richness or the high water conductivity found there. The results showed that streams associated with certified eucalypt plantations can exhibit good ecological quality and a significant aquatic biodiversity.