Impacts on aquatic ecosystem integrity of Portelo stream (Douro basin, NE Portugal) after a large spill of mining wastes
Artigo de Conferência
Visão geral
Visão geral
resumo
During December 2009, after a period of intense precipitation,
several millions of cubic meters of wastes from an abandoned
mine were spilled into Portelo stream, a tributary of Rio Sabor
(Douro basin) in the northeastern Montesinho Natural Park (NE
Portugal). The large amount of wastes covered the riverbed with
a layer of fine sediments, reaching more than half a meter in
areas close to the mine. Both riparian and agricultural areas were
also affected by these sediments from the mine. Wastes were
spilled downstream until the main watercourse, River Sabor, by
several strong rain events. This study, developed from 2010 to
2013, evaluated the impact of this event on ecosystem integrity,
namely in the water chemistry, channel and riparian habitats
and on macroinvertebrate communities. Samples were collected
from eight different stations distributed along the hydric system.
Toxicity experiments were developed in laboratory for one fish
species, the barbel (Luciobarbus bocagei), an endemic cyprinid
present in River Sabor. The results showed a substantial increase
of conductivity (>300 µS.cm-1), total suspended solids (> 100
mg.L) and a decrease of pH (<5) in the water analyses. From
the 52 elements analyzed, including different heavy metals, it
was detected a higher concentration of copper, aluminium and
cobalt in the water. Aquatic habitats were severely disturbed
and important changes occurred in riparian zone. Temporal
and spatial differences were found and several metrics (e.g.
taxonomic richness, diversity, evenness) confirming the
disturbance detected on macroinvertebrate assemblages. As
expected, the stations located near the mine showed the highest
levels of contamination and disturbance. Biochemical indicators
(Na+ and K+ plasmatic concentrations) used in laboratory
tests were sensitive, under acute copper exposure of barbel
populations (different copper concentrations, 0.06-0.48 ppm
were used), and can help to justify the disappearance and or
reduction of fish species in the affected area.
