Biochemical and physiological biomarkers in Prochilodus lineatus submitted to in situ tests in an urban stream in southern Brazil

Abstract

The aims of the present study were to verify the suitability of short-term in situ test with the neotropical fish Prochilodus lineatus and to evaluate from a set of biochemical and physiological biomarkers the ones which could work as sensitivity tools for the environmental quality assessment. In situ tests were carried out for 1 week in winter and summer, at three sites along an urban stream heavily contaminated by anthropogenic activities and at a reference site. The variables analyzed were: hemoglobin content (Hb), plasma concentrations of cortisol, glucose, total protein, Na⁺ and Cl⁻, plasma osmolarity, liver activities of glutathione-S-transferase (GST) and catalase and interrenal cells area. Results showed that glycemia, interrenal cell size and GST activity, which were significantly higher in fish caged in the urban stream, were best able to distinguish between the most disturbed sites and the reference and caged P. lineatus showed to be a promising tool for the assessment and monitoring of tropical aquatic ecosystems.

Introduction

In urban aquatic environments fish may be exposed to a myriad of substances at the same time produced by different kinds of anthropogenic activities. The exposure to two or more chemicals may result in biological reponses quantitatively or qualitatively different from that expected from the action of the chemicals alone (Rand et al., 1995). In Brazil, as in other developing countries, criteria for the classification of water courses are exclusively based on physical and chemical factors (CONAMA, 1992) and chemical analyses are normally restricted to identification of a limited range of contaminants in water, mainly metals, and provide little information concerning the presence of organic contaminants such as hydrocarbons and pesticides in water and sediment. Therefore, alternative methodologies for water quality assessment and environmental monitoring other than chemical monitoring are urgent needed (Bozzetti and Schulz, 2004).

In situ tests are useful tools in ecotoxicology, mainly because they integrate ecological relevance in toxicity testing, by incorporating field fluctuations in a cost-effective way (Castro et al., 2004). In this kind of field work, focusing on environmental quality, healthy organisms are taken to the field-site and exposed directly to the potentially contaminated environment (Stien et al., 1998, Pacheco and Santos, 1999, Parrot et al., 2000, Olsen et al., 2001, Pyle et al., 2001). Here, the actual situation is identified in the field and there is no need to extrapolate laboratory results to particular local conditions (Chappie and Burton, 1997). However, it is important to have in mind that despite providing a more realistic exposure regime, outdoor field tests do not provide more realistic concentration–response information than typically generated from laboratory tests (Graney et al., 1995).

Biological changes in fish that are related to the exposure or to the effects of contaminants are called biomarkers (Peakall, 1994) and their use has led to good results in environmental risk assessment (McCarthy and Shugart, 1990, Van der Oost et al., 2003). Prominent among these biomarkers are haematological data (Soivio et al., 1973, Sampath et al., 1993) and physiological variables, such as plasma levels of metabolites (Adams et al., 1990, DiGiulio et al., 1995) and ions (Engelhardt et al., 1981, Alkindi et al., 1996, Martinez and Souza, 2002), levels of hormones like cortisol (Hontela et al., 1996, Barton et al., 1998, Hontela, 1998, Benguira and Hontela, 2000) and biochemical variables such as detoxifying enzyme activities (Paris-Palacios et al., 2000, Teles et al., 2003, Ahmad et al., 2004). In order to make use of biomarkers its normal range of variation must be known; in other words, it is necessary to distinguish the natural variance of a given biomarker from altered values indicating stress due to contamination (Ranzani-Paiva et al., 2000, Olsen et al., 2001). In addition, the interfering effects of season on biomarkers must be elucidated, especially in tropical and subtropical regions, where interactions can be very complex (Wilhelm Filho, 1996).

In Brazil, there have been few field studies focusing on the use of native fish biomarkers as tools for water quality assessment (Wilhelm Filho et al., 2001, Winkaler et al., 2001, Martinez and Cólus, 2002, Martinez and Souza, 2002). The neotropical fish Prochilodus lineatus (Valenciennes, 1847) (=P. scrofa Steindachner, 1881), represents a well suited species to environmental monitoring as it is a bottom feeder fish which is in contact with xenobiotics in water and in sediment and also has been shown to be sensitive to variations in water quality (Mazon and Fernandes, 1999, Da Silva et al., 2004, Martinez et al., 2004).

Cambé stream and its tributaries constitute the main hydrological basin of Londrina, a city of 500,000 inhabitants in Paraná state, Southern Brazil; the Cambé crosses the entire city and is widely used for recreational purposes, despite being heavily impaired by anthropogenic activities. It receives diffuse and point source discharges of industrial, domestic and agricultural wastes since its headwaters. Previous chemical water analyses of the upper reaches of Cambé stream showed large amounts of metals, mainly lead and aluminum (Yabe and Oliveira, 1998). In addition, Winkaler et al. (2001) showed that feral fish from these upper areas present impaired health and more recently, Lemos et al. (2005) demonstrated that its water induces DNA damage, detected by comet assay.

Thus, the objectives of the present study were to verify the suitability of a short-term in situ test with Prochilodus lineatus and to evaluate from a set of biochemical and physiological biomarkers the ones which could work as sensitive tools for the assessment of the environmental quality of Cambé stream.