A. Pinto
1
, A. Coimbra
1
, S. Ribeiro
1
, J. Carrola
1
, R. Cortes
2
, A. Fontainhas-Fernandes
1
,
S. M. Monteiro
1
1 Department of Biology and Environment, School of Life and Environmental Sciences;
2 Department of Forest and Landscape, School of Agriculture and Veterinary Sciences,
University of Trás-os-Montes e Alto Douro, Centre for the Research and Technology of
Agro-Environmental and Biological Sciences, Vila Real, Portugal presenting author's contact: smonteir@utad.pt
Over the last years, the urban, industrial and agricultural development of the northwestern Portugal region, significantly increased the continuous effluent discharges to watercourses. A biomarker-based monitoring is a promising approach to assess the effect of these contaminants on fish health, providing both early-warning signs of acute pollutants exposure, and chronic toxicological impacts. Gills are particularly susceptible to chemical exposure due to their large surface area and weak detoxification system.
Therefore, gill histopathological changes and biochemical responses constitute potential biomarkers of contaminants exposure.
In order to determine how these biological responses answer to contamination gradients, in the present study, different gill biomarkers were assessed in the native fish species, Luciobarbus bocagei , Squalius carolitertii and Pseudochondrostoma sp..
Fish were captured during winter and summer of 2012, in different locations, covering an ecological quality gradient, from reference conditions to highly disturbed. Gills were sampled and processed for light microscopy and biochemical determinations. The main gill histopathological changes observed were lamellar fusion (LF), filament (FEP) and lamellar (LEP) epithelium proliferation, vasodilatation (Va), aneurisms (An), edema
(Ed), lifting (Lif) and necrosis (Ne). In all species, the prevalence values of FEP clearly reflected a pollution gradient among the different places, and were generally higher in the winter. The quantitative evaluation of the histopathological changes showed that, in
L. bocagei , the severity gradation scale of LF, FEP, LEP, Va, Lif and Ne revealed higher levels of severity in polluted sites, while in S. carolitertii , FEP, Va, An and Ed were the lesions that showed greater severity in polluted sites in comparison to reference ones. In Pseudochondrostoma , the severity level of LF, LEP, An, Ed and Lif increased with the worsening of the ecological condition.
In general, all species showed inferior lipid peroxidation levels in locations previously classified with bad ecological status. On the other hand, Glutathione-S-
Transferase, that protects against lipid peroxidation, and Catalase activities increased with the pollution degree. The Glutathione Peroxidase activity, in S. carolitertii , decreased with the pollution gradient, although in Pseudochondrostoma the opposite profile was observed. Pseudochondrostoma was the species that better reflected the ecological status.