Metal bioavailability and distribution in the fish community in a tropical estuary, Sepetiba Bay, Rio de Janeiro, Brazil

Sepetiba Bay has a wealth of fish species (total 148) as well as a vast area of mangroves and numerous rocky islands, which are important sites of reproduction for marine life. This peculiar environment of the Brazilian coast hosts one of the most important industrial centres of south-eastern Brazil. This site has been impacted for decades by the release of industrial emissions and effluents with high metal loads by the steel industry. The ranges of metal concentrations in fish muscle from the species Micropogonias furnieri, Genidens genidens, Cathorops spixii, Notarius grandicassis, Diapterus rhombeus, Selene vomer, Prionotus punctatus, Citharichthys spilopterus, Achirus lineatus, Trinectes paulistanus, Symphurus tessellatus and Hypanus guttatus were measured (Al: 0.02-555.9 µg g-1 d.w., As: 0.0002-20.1 µg g-1 d.w., Cd: <0.0002-0.2 µg g-1 d.w., Cu: 0.2-2.3 µg g-1 d.w., Fe: <0.02-244.9 µg g-1 d.w., Zn: 0.5-227.3 µg g-1 d.w. and Pb: <0.001-1.3 µg g-1 d.w.). The Kruskal-Wallis test revealed significant differences (p<0.05) in the As, Cu, Fe, Pb and Zn contents among fish species. The monitoring of suspended particulate matter during dredging operation revealed the mean metal values for Al (6059±6268 µg g-1), Cd (0.2±0.5 µg g-1), Cu (29±29 µg g-1), Zn (332±892 µg g-1), and Pb (52±70 µg g-1). The results of bioaccumulation in fish calculated from the bioavailable sediment fractions and suspended particulate matter showed lower values than those in fish muscle. Arsenic was found at levels above the maximum limit for human consumption according to Brazilian legislation. However, the estimated probability and risk of metal intake via fish consumption showed that the consumption of all species presented low risk.

Opsanus beta (Goode & Bean, 1880) (Acanthopterygii: Batrachoididae), a non-indigenous toadfish in Sepetiba Bay, south-eastern Brazil

The introduction of non-native predator fish is thought to have important negative effects on native prey populations. Opsanus beta is a non-native toadfish that was originally described in the Gulf of Mexico, between the west coast of Florida and Belize. In the present study, we describe, for the first time, the occurrence of O. beta in Sepetiba Bay (22°55′S), south-eastern Brazil, probably brought into the bay through ships' ballast water. Thirteen specimens were recorded in this area near to Sepetiba Port. Similarly, three other records of this species in the Brazilian coast were also reported near to port areas at Rio de Janeiro (22°49′S), Santos (23°59′S) and Paranaguá (25°33′S) ports. To confirm the species identity, we employed DNA barcoding and compared our samples with sequences deposited on public databases, which indicated that our samples are highly similar (>99.9% of genetic similarity) to O. beta samples collected near its type locality. Several individuals were found in the capable spawning phase, according to histological analysis of the reproductive cell stages. The environmental plasticity of this species and the favourable local environmental conditions probably enabled the establishment of O. beta in this region. This raises concerns of potential high invasion impact due to this species' diet and reproductive capacity.

Assessing the histological changes in fish gills as environmental bioindicators in Paraty and Sepetiba bays in Rio de Janeiro, Brazil

The use of fish species uses as bioindicators is an important environmental monitoring tool. Histological biomarkers are adopted to assess the health conditions of different organisms and to indicate an environmental hazard. Histology can be applied as an effective method to analyze the effects of pollutants and other stressors. Accordingly, histological changes in the gill epithelium were analyzed to assess the adoption of fish species Menticirrhus americanus (Linnaeus, 1758) and Micropogonias furnieri (Desmarest, 1823) as a bioindicator to measure environmental quality in Paraty and Sepetiba bays, in Rio de Janeiro. A random sample of 58 fish was collected from the assessed bays. We found Paraty Bay to be in good conservation condition, whereas Sepetiba Bay is contaminated. The fish species collected from Sepetiba Bay showed lesions such as epithelial lifting, aneurysm, and necrosis in the gills; thus, it was possible to suggest that histological biomarkers be used bioindicators to measure the environmental impact in these bays.