Biomonitoramento da contaminação por metais em estuários cearenses utilizando moluscos bivalves: uma análise integrada de sedimentos e organismos

Abstract

This study evaluated the contamination by trace metals (Cd, Cu, Pb, and Zn) and their bioavailability in three estuaries in Ceará (Brazil) with distinct levels of anthropogenic impact: Pacoti (slightly eutrophic), Jaguaribe (eutrophic), and Cocó (eutrophic and urban). The approach integrated the analysis of metals in the soft tissues of six bivalve species (Anomalocardia flexuosa, Austromacoma constricta, Iphigenia brasiliensis, Tagelus plebeius, Phacoides pectinatus, and Myella strigata) with the mobility of metals (labile and refractory fractions) in the fine fraction (<125 μm) of the sediment. Concentrations in organisms and sediment were determined by atomic absorption spectrometry after acid digestion. The results indicated that bioaccumulation in bivalves is more closely related to the concentration of metals in the labile fraction of the sediment than to the total concentration. The species exhibited distinct responses to contamination, influenced by their physiology and detoxification strategies. Anomalocardia flexuosa confirmed its potential as a widely distributed biomonitor, while Phacoides pectinatus demonstrated high sensitivity and bioaccumulation of Pb, standing out as a promising candidate for more specific monitoring. Concentrations of Cu and Pb in some organisms were recorded above the limits established for consumption by Brazilian legislation, indicating a potential risk to public health. This study provides pioneering data for the Cocó estuary and reinforces the importance of analyzing metal mobility in sediments for a realistic assessment of risk and the effectiveness of biomonitoring in tropical estuarine environments.