3rd meeting of young researchers at UP 1 - IJUP - Universidade do ...

Ecological Assessment of Leça river:
Sediment and habitat study
C. Café 1 , A. Mucha 2 1, 2
, A. A. Bordalo
1 Laboratory of Hydrobiology, Institute of Biomedical Sciences, University of Porto, Portugal
2 CIIMAR – Centre of Marine and Environmental Research, University of Porto, Portugal
One of the main purposes of the European Water Framework Directive (WFD) is the
establishment of standards for the ecological characterization and protection of all surface
waters, towards the “good ecological status” of the systems. This classification is based on
monitoring the ecosystems by using a multidisciplinary approach, and the yielded knowledge
used to draw management and remediation strategies based on the river basin concept. This
study was an assessment of the ecological status of habitats of the Leça River, in the north part
of Portugal. Roughly half of its 50 km course, in the upstream stretch, is rural, being the
remaining portion highly influenced by the densely populated Metropolitan Area of Porto.
Sampling took place in June and July 2008, and the study included an assessment of benthic
macroinvertebrate community and sediment characteristics, such as grain size, amount of
organic matter, redox potencial, organic and metal toxicity and denitrification potential in
eleven locations along the river. Data analysis was performed using PRIMER ® , PCA was used
to analyze environmental data, MDS was used to analyze biological data, and BIO-ENV
procedure was used to establish correlation between sediment characteristics and biological
data. Also, the overall habitat status was evaluated using River Habitat Survey, a method for
classifying rivers according to their habitat quality and modification. There was a clear
distinction in the characteristics of sediment of upstream and downstream stations, revealing
the growing organic contamination gradient towards the mouth. Those stretches presented the
highest values for the environmental variables analyzed, namely organic matter, redox
potential and organic toxicity, as well as the most similar benthic communities, dominated by
highly pollution-resistant organisms. The results of the River Habitat Survey varied between
“Very Poor” and “Poor” Habitat Quality and between “Semi-natural” and “Obviously
Modified” status of the channel. The results show the need to implement a sustainable plan for
the recovery of the river in the vein of the WFD.
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