Avaliação de risco ecotoxicológico de três estuários do litoral do Ceará, Nordeste do Brasil

Abstract

The estuaries and the coastal areas are particularly vulnerable to anthropic activities installed at their catchments, because such areas represent the fate of several substances that are harmful to the natural ecosystems and the local biota. Anthropic pressures in the estuary of the rivers Ceará (ERC), Pacoti (ERP) and Jaguaribe (ERJ), at Ceará State, Northeastern Brazil, intensified the input of contaminants into these ecosystems. Contamination by metals (Al, Cr, Cu, Fe, Hg, Pb and Zn) and poli-aromatic hydrocarbons (PAHs) have been reported, mainly to the ERC, which is widely impacted by urban and industrial effluents. Other studies on the ERJ indicated environmental degradation due to effluents from shrimp farming, while urban effluents are the main sources of contamination to the ERP, which was considered unpolluted until the early 2000s. The few investigations about the ecotoxicological effects in these estuaries were punctual and revealed the occurrence of acute and chronic toxicity, with more severe effects on the ERC. The present study aimed to assess the ecological risk of the estuaries of Ceará, Pacoti and Jaguaribe, by integrating analyzes of physiological conditions, biomarkers and bioaccumulation in catfish, and analysis of mercury concentration in the sediment of ERC, ERP and ERJ. The occurrence of ecotoxicological damage in animals was assessed by biochemical, histological and genotoxic biomarkers, bioaccumulation of Hg, condition factor and somatic indices in catfish Sciades parkeri and S. proops from the ERC, and S. herzbergii from the ERP and ERJ. Fish were collected between June 2011 and November 2012, sacrificed and their tissues were removed and stored for analysis. Sediments of three estuaries were collected for mercury quantification. Damages concerning the depuration processes of xenobiotics were more expressive in catfish from ERP and ERJ, while morphological damage was evident in fish from ERC. The bioaccumulation of mercury in soft tissues was higher among fish from ERP and ERJ, although the concentrations in sediments were higher in ERC. The estuaries of ERC, ERP and ERJ are under ecological risk and demand actions for the identification, monitoring and control of pollution sources. Through integration of the different lines of evidence, the ecological risks can be classified as severe for the ERC and from moderate to severe for the ERP and the ERJ.