The Cichlidae fish Geophagus brasiliensis (Quoy & Gaimard, 1824) has suitability as a sentinel species for changes caused by xenobiotics?

Industrial wastewater and agricultural practices are among the main activities discharging organic pollutants, such as Polychlorinated biphenyl (PCB) congeners and organochlorine insecticides (e.g. DDT - dichloro diphenyl trichloroethane), to the environment. In this study, we used the native Cichlidae fish species Geophagus brasiliensis as a sentinel to evaluate the hepatic 7-ethoxyresorufin-O-deethylase EROD activity, a biomarker of exposure to CYP1A-inducing pollutants, to assess the bioavailability of xenobiotics in two reaches of a large lotic system in Southeast Brazil: a less disturbed area (site 1) in the upper stretch, and an area in the middle stretch, which receives various industrial and agricultural effluents from upstream cities (site 2). In addition, G. brasiliensis were exposed to a single dose of 50 mg kg-1 beta-naphthoflavone (BNF) or of 50 mg kg-1 dimethylbenzoanthracene (DMBA) to test the effects on, respectively, the hepatic EROD activity in S9 supernatant fraction, and the frequency of micronucleated erythrocytes three days after the i.p. treatments, and compared to an unexposed group, to test its potential as a sentinel for biomonitoring studies. The EROD activity was approximately two-fold higher in fish from the impacted stretches than in fish from the less disturbed stretches (p < 0.05). Micronuclei (MN) frequency was also significantly different (p < 0.01) in DMBA-treated fish. The induced EROD activity in the impacted site suggests that organochlorinated pollutants are reaching the biota of the Paraíba do Sul River, confirming the suitability of Geophagus brasiliensis as a useful sentinel species to detect changes caused by xenobiotics(AU)

Assessing of biotic integrity of the fish community in a heavily impacted segment of a tropical river in Brazil

A index of biotic integrity (IBI) was applied to assess the ecological health at seven sites of ca. 338 km extension of the Paraíba do Sul river, in bracketing a large urban-industrial complex. The aim was to evaluate the index response to changes in environmental quality during two seasons (winter/dry versus. summer/wet). Eight metrics were selected to IBI in three categories: 1) species richness and habitat composition; 2) indicator species; and 3) trophic structure. The IBI, based on the least impacted regional condition, showed the highest value at the most upstream site (Queluz=km 0) - Acceptable, then decreasing downstream and reaching the lowest record at Volta Redonda (km 125) - Impacted; afterwards there was an increasing quality toward the most downstream sites until reaching better scores at Além Paraíba (km 338) - Moderate Impacted/ Acceptable. During the winter/dry seasons a clearer spatial trend was detected when compared with oscillations in summer/wet. The IBI proved to be a suitable tool to evaluate environmental quality in this tropical and very altered large river, since it was sensitive to non-source point pollution changes, which occurred all over the studied area.

O índice de Integridade Biótica (IBI) foi aplicado em sete locais do rio Paraíba do Sul, cobrindo uma extensão de 338 km, e incorporando um trecho de grande densidade industrial. O objetivo foi avaliar a resposta do índice às mudanças na qualidade ambiental durante dois períodos (inverno/seco versus verão/úmido). O IBI foi determinado através de oito métricas compreendidas em três categorias da comunidade de peixes: 1) riqueza de espécies e composição de habitats; 2) espécies indicadoras; e 3) estrutura trófica. Utilizou-se a condição menos impactada da região como abordagem para a comparação dos locais, com os mais altos valores ocorrendo nos locais mais a montante (Queluz=km 0) - Aceitável, diminuindo mais abaixo e atingindo os piores valores em Volta Redonda (km 125) - Impactado; uma subseqüente melhoria ocorreu nos locais mais a jusante, atingindo melhores valores em Além Paraíba (km 338) - Moderadamente Impactado/Aceitável. Durante o período inverno/seco foi detectado uma clara tendência espacial quando comparado com as oscilações registradas no verão/úmido. O IBI provou ser uma ferramenta adequada para avaliar a qualidade ambiental nos grandes rios tropicais que se encontram em elevado estágio de alteração, já que se mostrou sensível às variações na poluição difusa que ocorre ao longo de toda área estudada.

A preliminary index of biotic integrity for monitoring the condition of the Rio Paraiba do Sul, southeast Brazil.

The biodiversity of many Brazilian rivers is seriously threatened by industrial and municipal pollution, and Rio Paraiba do Sul, located between two major industrial centers is one example of this situation. A survey of the fish assemblage was conducted from October 1998 to September 1999 and the data were used to develop an index of biotic integrity (IBI). We sampled three zones in bracketing a large urban-industrial complex to evaluate water quality changes and the usefulness of the IBI as a monitoring tool. Water quality was classified as poor upstream of the effluent discharges, very poor near the discharges, and poor-fair downstream of the discharges, with this latter situation revealing the current biological capacity of the river. Physical and chemical habitat characteristics were also measured at each site to construct an independent environmental index to validate the IBI. The habitat and IBI indices were highly correlated, suggesting this IBI would be applicable to other large rivers in southeast Brazil.