Utilização de ferramentas biogeoquímicas como indicadoras do status de saúde de dois estuários tropicais no Nordeste do Brasil

Abstract

The marine and estuarine ecosystems of the Brazilian coast form a mosaic of environments interconnected through energy flow and by species that occupy different habitats throughout their life cycle, sustaining numerous economic activities such as fishing or tourism. The Northeast is one of the most densely populated coastal regions of Brazil, standing out for urbanization and degradation of ecosystems, the result of multiple impacts, mainly due to domestic pollution, agro-industrial activity, and habitat modification around major urban centers. The present study aimed to use different complementary techniques to diagnose the environmental quality of two tropical estuaries in Pernambuco, Northeast Brazil: the estuary of Barra de Sirinhaém (SIR), on the southern coast of Pernambuco and the estuary of Canal de Santa Cruz (ITAP), northern coast. As tools for this diagnosis were used the integration of biological and geochemical tools through the measurement of metals in fish and sediment, the use of histopathological biomarkers in gills and liver, and application of isoscape associated with δ13C and δ15N isotopes as biomarkers of pollution through organic matter in sediment (SOM). In Chapter 1, we evaluated the concentrations of trace metals in fish (Bardiella ronchus, Caranx latus, Centropomus undecimalis, Centropomus parallelus and Gobionellus stomatus) and in sediment, from the abiotic matrix we observed that, in SIR, the contamination is at the alert level only for Cu according to the Canadian Sediment Quality Guide, and the other metals (Cd, Cr Hg, Pb and Zn) are classified as with low probability of causing effects in biota. In ITAP, the metals Cd, Cr, Pb and Zn in the sediment were classified as low probability to cause deleterious effects on biota. Additionally, by using various indices applied to the sediment and through metal concentration in fish, low risk was also observed through the ecological risk assessment. However, Cu and especially Hg contamination was observed in ITAP, and this persistent impact of Hg was reflected with values above the allowable for fish ingestion in the species Centropomus undecimalis and Bardiella ronchus. In Chapter 2, using histopathological biomarkers, it was observed that the effects of these metals and the other contaminants present in the estuaries, SIR and ITAP, resulted in an impact with a degree and severity of severe injury to fish. In chapter 3 we used stable isotope δ13C and δ15N with the mixing and isoscape models applied to sediment and fish to assess the anthropogenic impacts present in SIR. Using these techniques, it was observed that the isotopic signature of the SOM for δ13C was higher in the upper estuary near the sugarcane industry and other domestic effluents, compared to the lower estuary near the sea. The δ15N of the SOM varied spatially in the estuary being higher in the lower estuary due to the sugarcane industry effluents transported from the upper part of the estuary and the effluent discharge. These tools were suitable as a form of biomonitoring, especially the mixing model to evaluate the contribution of regions with higher inputs of contaminants in the diet of C. undecimalis, C. paralleus and Caranx latus. Based on the three chapters, the species have ideal attributes to be used as biomonitors of contamination, especially the species C. undecimalis and C. paralleus. All methodologies and analyses performed converged to the same result. The ITAP is potentially more contaminated than the SIR, the latter being considered a region with low impact. This thesis used efficient techniques that are easily applicable and replicable in other areas of study in order to provide subsidies for the environmental management of estuaries and the effects of pollution on biota, as well as relevance to the advancement of research in the area of fishery resources and aquaculture.