Accumulation and distribution of metals in the tissues of two catfish species from Cananéia and Santos-São Vicente estuaries

BRAZILIAN JOURNAL OF OCEANOGRAPHY, 60(4):463-472, 2012 ACCUMULATION AND DISTRIBUTION OF METALS IN THE TISSUES OF TWO CATFISH SPECIES FROM CANANÉIA AND SANTOS-SÃO VICENTE ESTUARIES Juliana de Souza Azevedo*, Marcos Antônio Hortellani and Jorge Eduardo de Souza Sarkis Instituto de Pesquisas Energéticas e Nucleares, Centro de Química e Meio Ambiente (Av. Prof. Lineu Prestes, 224, São Paulo, SP, Brasil) *Corresponding author: A BSTRACT Pb, Cd, Zn, and Cu concentrations and their distribution in liver, gill, and muscle tissues of the catfish Cathorops spixii and Genidens genidens were investigated in order to provide information concerning the bioaccumulation processes in these species. Fish were collected in one estuary subject to slight human influence (Cananéia) and in two regions within the Santos-São Vicente estuary, São Paulo, Brazil, subject to distinct anthropogenic influences: 1) industrial and 2) domestic. In general, the highest concentrations of Cu, Zn, Cd, and Pb were found in the liver tissue. Muscle showed the lowest values of metal accumulation for all the elements investigated. Regarding the distribution and the metal pollution index (MPI), the levels of the metals analyzed decreased in the following order: liver>gill>muscle. MPI results suggest that gill and liver are important organs to exemplify the bioaccumulation process and are also better able to reflect both recent and chronic exposure to metals. R ESUMO Concentrações de Pb, Cd, Zn e Cu e sua distribuição no fígado, brânquias e músculo dos bagres Cathorops spixii e Genidens genidens foram determinadas visando fornecer informações sobre os processos de bioacumulação desses metais nas espécies. Os peixes foram coletados no estuário de Cananéia e em duas regiões do estuário de Santos-São Vicente, ambos em São Paulo, Brasil. Esses estuários apresentam distintas influências antropogênicas, sendo o primeiro deles submetido a impacto industrial e o segundo a impacto doméstico. Em geral, as maiores concentrações de Cu, Zn, Cd e Pb foram obtidas no tecido hepático. No músculo foram encontrados os menores valores de acumulação para todos os elementos investigados. Quanto à distribuição dos metais e ao seu índice de poluição (Índice de Poluição por Metais- IPM), os níveis diminuíram na seguinte ordem: fígado>brânquias>músculo. Resultados do IPM sugerem que as brânquias e o fígado são importantes órgãos para indicar processos de bioacumulação, sendo também os melhores para refletir exposições crônica e recente a metais. Descriptors: Bioaccumulation, essential and non-essential metals, Metal pollution index, Estuaries, Cathorops spixii, Genidens genidens. Descritores: Bioacumulação, Metais essenciais e não essenciais, Índice de poluição por metais, Estuários, Cathorops spixii, Genidens genidens. INTRODUCTION The characterization of the accumulation of metals in different organs or body compartments in fish has proved to be a representative measure of exposure (SERAFIM; BEBIANNO, 2001) and is used to monitor the bioavailability of these pollutants (KNAPEN et al., 2007). The distribution of metals within the body of a fish may vary considerably, depending on the species (HEATH, 1990). Muscles are not always a good indicator for the whole body, but can indicate chronic exposure (JARÍC et al., 2011). It is possible to identify different excretion routes of harmful chemicals in fish, including the gills, bile, kidney and skin. The mechanism of metal uptake through the gills is most likely one of simple diffusion, possibly through pores. There is no evidence of active transport of metals through fish gills, although there may be cases of carrier mediation. The liver’s function is that of regulating metal homeostasis in fish, and it plays an important role in the detoxification, accumulation and excretion processes. Some metaloproteins are known by their function in detoxification. Metallothionein (MT) is a low molecular-weight protein which has many sulfhydryl groups that bind a variety of metals 464 BRAZILIAN JOURNAL OF OCEANOGRAPHY, 60(4), 2012 and, therefore, make them less toxic to other cellular constituents (HEATH, 1990). With the liver’s tendency to accumulate several metals, the association of large amounts of MT with this tissue is not surprising. Zn and Cu are known as essential elements that activate many enzymatic systems. Zn especially has an important function since it is a component of metallothionein. This latter protein is very important in the detoxification of toxic metals through the dismutation of zinc-binding by, for example, Cd and Cu (although at lower levels, Cu also has a significant importance in MT metal-biding). In contrast to Zn, Cu and Cd, there is no evidence that Pb produces the metal-binding protein metallothionein (SMIRNOV et al., 2005). Metals such as zinc (Zn) and copper (Cu) are essential to the metabolism of living organisms such as fish, while some others such as lead (Pb) and cadmium (Cd) play an unknown role in biological systems and have, therefore, been extensively studied (DURAL et al., 2007; KARADEDE-AKIN; ÜNLÜ, 2007; YILMAZ et al., 2010; JARÍC et al., 2011). Essential and non-essential metals must be collected from water, sediment, or food, especially in the feeding of benthic-foraging fish. However, the metals in sediments are not always bioavailable, since their bioavailability depends on a series of factors such as pH, Eh, granulometry and organic matter content. Nonetheless, metals in the environment are taken up by fish and can accumulate in tissues such as muscle and liver (HEATH, 1990). The Santos-São Vicente estuary is located in the central coastal area of Brazil in the southeastern area of São Paulo state. Industrial activities and tourism are economically important to the region and its dense population produces large quantities of domestic sewage. This estuary also contains the largest commercial harbor in South America and, with approximately 1100 industries (such as fertilizers and pharmaceuticals), it is one of the most important petrochemical and metallurgical industrial areas in Brazil. Some authors have reported high concentrations of different chemical pollutants, for instance metals such as Pb, Cd, Zn and Cu introduced into this coastal aquatic system as a result of the various industrial activities undertaken in the inner area of the estuary (BOLDRINI; NAVASPEREIRA, 1987; AZEVEDO et al., 2011; AZEVEDO et al., 2012a). The rapid increase in urbanization and industrialization, mainly in the last 50 years, has led to the degradation of the coastal mangrove habitat through contamination with effluents from industrial and domestic sources and solid waste. All of these anthropogenic sources contribute directly or indirectly to the concentration of metal contaminants in the local environment. Unlike that of Santos-São Vicente, the Cananéia estuary is subject to slight anthropogenic influence and is frequently used as an example of a non-impacted (...truncated)