Abstract
The variations in size and spatial and temporal variations in concentrations of toxic metals (cadmium, mercury, and lead) in oyster tissues were studied. Samples were collected at monthly intervals over a 1-year period from three locations along the southern coast of Oman (Mirbat, Hadbeen, and Sadah). Cadmium and lead were analyzed using an inductively coupled plasma atomic emission spectrometer, and mercury was analyzed using a direct mercury analyzer. The annual mean concentrations in oyster tissues sampled from the three locations and from different time periods ranged from 2.64 to 3.80 mg kg-1 for cadmium, 0.009 to 0.02 mg kg-1 for lead, and 0.01 to 0.02 mg kg-1 for mercury. The temporal effect on cadmium concentrations was more distinct than the local site-specific effect, with higher concentrations recorded in tissues during the summer season than in the winter season. Moreover, within each site, a significant time-specific dependence on the toxic metal concentration differences was recorded. Lipid content was found to influence mercury concentrations in the oysters; however, there was no relationship between cadmium or lead and moisture or lipid content. No distinct relationships were observed between the size of oysters and metal uptake by the oyster. The results were discussed in relation to those obtained from related species in the seas of Oman and worldwide.
Highlights
Mercury, cadmium, and lead are the major toxic metals that cause environmental degradation in marine ecosystems (Matta et al 1999)
Annual mean metal concentration The calculated annual mean concentrations of mercury, cadmium and lead in rock oyster collected from the Dhofar coastal areas in the Arabian Sea from June 2009 to May 2010 were 0.017 ± 0.008 mg kg-1, 3.31 ± 1.14 mg kg-1, and 0.011 ± 0.03 mg kg-1, respectively
It has been well documented that the rock oyster, S. cucullata, is capable of bioaccumulating toxic metals in its soft tissues and metal concentrations within this study were, on average, within the variations commonly described in the literature for natural areas or areas slightly affected by metal pollution (Table 1)
Summary
Cadmium, and lead are the major toxic metals that cause environmental degradation in marine ecosystems (Matta et al 1999). Toxic metals are introduced into the marine environment by natural and anthropogenic activities (O’Conner 1996). These metals accumulate in the bodies of marine biota at concentrations much higher than those found in the ambient water and are biomagnified in the food chain at higher trophic levels, posing a risk to human consumers (Saka et al 2006). Bivalves are widely used as indicators to assess the bioavailability of metals in coastal waters in many parts of the world (Blackmore 2001; Cohen et al 2001; Sunlu 2002), because of their trophic level may accumulate pollutants differently because of differences in the physical and chemical properties of the habitat (Chouvelon et al 2009). Oysters have already been proposed as a biomonitor for marine ecological tests to assess the water quality because of their sensitive nature and rapid response to pollutants (Szefer 2002; Phillips 1990). We attempted to understand the real situation of toxic metal accumulation in edible oyster tissues in Oman by using a 1-year dataset
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