Bioacumulação dos metais mercúrio e cobre na ostra do mangue Crassostrea rhizophorae (Guilding, 1828) na bacia inferior do rio Jaguaribe (CE)

Abstract

The bioaccumulation consists in absorption rates of contaminants by organisms faster than desorption rates. In the Jaguaribe River estuary, contagious activities such as intensive shrimp aquaculture, agriculture, husbandry, and urbanization, contribute for the degradation of the estuarine region by means of discharge of effluents without proper treatment, containing metals such as copper (Cu) and mercury (Hg). The present study aimed to use the mangrove oyster, Crassostrea rhizophorae, as biomoitor of these metals along the lower basin of Jaguaribe Rivers in three sites under different levels of exposure to anthropogenic actions. Samples were collected from three sites potentially under different levels of exposure to anthropogenic actions. Samples were digested in a microwave (MARS XPRESS – CEM) and the quantification of Hg was done by cold vapor atomic absorption spectrophotometry in a CVAAS, NIC RA-3 model of NIPPON, whereas the quantification of Cu occurred by conventional flame atomic absorption spectrophotometry in a Schimatzu AA-6200 model spectrophotometry. The results showed the highest average Hg concentrations in the Amor channel station (51, 9 + 8,9 ng.g-1 ) and for Cu in the Ilha station (67,0 + 4,3 µg.g-1 ). Lowest Hg and Cu were observed in the Cumbe channel station: 21, 3 ± 2,3 ng.g-1 and 33,9 ± 1,9 µg.g-1 , respectively, despite being the station that receives directly the effluents of a large extension of shrimp farms. In comparison with results obtained previously in oyster from the Jaguaribe river estuary, there was a light decrease of concentrations of Hg, while for Cu there was a significant increase in over time. The maximum values reported for Cu concentrations were higher than the legal limits for human, while Hg presented lower concentrations although it is necessary to continue maintaining monitoring for the human consumption of mollusc.