Biomarcadores de efeito e parasitológicos em peixes nativos para avaliação ambiental de dois lagos da baixada maranhense, Amazônia oriental

Abstract

The biomonitoring of environmental quality is essential for evaluating the relationship between pollutants, organisms, and their effects, which can indicate the association of environmental degradation with parasitic activity in fish, affecting the epidemiological triad (host-parasite-environment). This can result in economic losses in fishing, food security issues, and public health risks due to the zoonotic potential of some parasites and the presence of pollutants. Thus, biomarkers of effect and parasitological parameters were evaluated in three species of native fish from the Açu and Viana lakes in the Baixada Maranhense, Eastern Amazon, during two seasonal periods. Microbiological, physical, and chemical data from the surface waters of the lakes were measured at three sampling points (P1, P2, and P3). Additionally, water, sediment, and fish muscle samples were collected for microbiological analyses, total coliform quantification, Escherichia coli, and trace elements. A total of 240 fish of the species Hoplias malabaricus, Pygocentrus nattereri, and Prochilodus lacustris were collected from the lakes for micronucleus (MN) testing, determination of the Histological Alteration Index (HAI) in gills and liver, and parasitic fauna collection. Water parameters pH, dissolved oxygen (OD), and E. coli showed values outside the recommended limits by CONAMA 357/2005 and 430/2011 regulations. Total coliforms and E. coli were found in all water samples, with higher values in Lake Açu in both seasonal periods. Metals Al>Fe>Cu>Mn>Pb>Hg>Se and Al>Fe>Mn>Cu>Pb>Hg>Se were found in water, sediment, and fish muscle, with higher values during the dry season. There was a significant difference (p<0.05) for MNi, higher during the dry season for both lakes and all three species, being 0.8% for H. malabaricus, 0.4% for P. nattereri, and 0.6% for P. lacustris. Erythrocytic nuclear alterations were more significant during the rainy season, especially notching. There was a correlation between the metals found in water and sediment samples with erythrocytic nuclear alterations, indicating that metal concentrations in these ecosystems can affect fish health. Histological alterations in the gills and livers of fish showed higher HAI values during the dry season. There was a statistical difference in gills for P. nattereri (p<0,0001) in Lake Açu and in the liver for P. lacustris (p<0,0001) and P. nattereri (p=0.03) in Lake Açu and P. nattereri (p=0,049) in Lake Viana. Parasites Contracaecum sp. and Procamallanus sp. were found in the internal cavities, liver, and fat region of the fish, isopod Braga patagonica in the gill cavities, pelvic and lateral fins, as well as Trypanosoma sp., Myxobolus sp., and Haemogregarina sp. in the fish blood. In summary, this study highlights the importance of environmental monitoring of lakes and fish health to identify risks to the population and the ecosystem. The data will support future research and protective measures, emphasizing the need to understand and conserve the lacustrine environments of the Baixada Maranhense Protected Area