Trace metals in water, sediment and bivalves of a tropical estuary, west coast of India

Baseline health risk assessment of trace metals in bivalve shellfish from commercial growing areas in the estuaries of Ashtamudi and Vembanad (Kerala, India)

Trace metal concentrations were monitored in the yellow clam (Paphia malabarica), green mussel (Perna viridis) and edible oyster (Crassostrea madrasensis) from growing areas in the Ashtamudi and Vembanad estuaries, Kerala. Samples of shellfish (clams n=26, mussels n=18, oysters n=36) and environmental parameters (salinity, temperature, pH and rainfall) were measured in these growing areas from July 2012 to December 2014. Ranges of mean annual concentrations (mg/kg) were Ni (0.46-0.65); Co (2.87-3.49); Fe (80.0-119.4); Mn (3.88-9.38); Zn (40.8-76.2); Pb (1.28-2.00); and Cu (1.59-4.38). In Ashtamudi, clams had higher mean concentrations of Ni, Co, Fe, Mn and Pb than oysters. Mean concentrations of Ni, Pb (in all species), Zn (in clams and mussels) and Cu (in mussels) did not exceed maximum permissible limits mandated by the Food Safety and Standards Authority of India. Mean Mn concentrations exceeded the World Health Organization guideline (1 mg/kg) in the three species while mean Fe concentrations in clams and oysters did not exceed the guideline (100 mg/kg). Target hazard quotients were generally ≤ 1, except for a few Pb results in clams and mussels. Although results suggest no health risk to consumers for the reference doses, daily intakes and elements considered, regular monitoring of trace metals is recommended to maintain consumer protection given increasing anthropogenic and climatic pressures on the shellfish growing areas.

Snapshot of environmental condition in different tropical estuarine systems by using S. cucullata (an edible oyster) as bio-indicator

Accumulation of toxic metals and indigenous bacteria in oyster, (Saccostrea cucullata) and their impact on antioxidant enzyme activities in the biological system was studied and used to provide snapshot of environmental condition in different tropical estuarine systems. The sedimentary Cd, Pb, and Hg concentration varied from 0.1 to 1.8, 22.0 to 98.0, and 0.03 to 0.11 mg kg^-1 (dry wt.) respectively. The bioaccumulated Cd, Pb, and Hg concentration in the oysters ranged from 3.6 to 9.0, 0.03 to 8.0, and 0.06 to 0.1 mg kg^-1 (dry wt.) respectively. In the oyster, the Cd concentration was well above the safe limit whereas the Pb and Hg concentrations were below the safe limit recommended by the European Commission (EC No. 1881/2006) for human consumption. The MPN value in the raw oyster for fecal coliforms (33-110 × 10³/100 g) exceeded the United States Food and Drug Administration (USFDA) approved limits. Increase in antioxidant enzymes (catalase, superoxide dismutase, glutathione-s-transferase, and metallothionein) activities with increasing pollutants loading was observed. The activities of antioxidant enzymes in the oyster were found to be very useful tool for evaluating environmental condition in any tropical estuarine systems.

Heavy metal concentrations in some gastropods and bivalves collected from the fishing zone of South India

The present study investigates heavy metal concentrations in gastropods and bivalves collected from major fishing centers in South India. Three gastropods, Bursa spinosa, Tibia curta, and Murex trapa, and two bivalves, Perna viridis and Villoritta cyprinoids, were collected for the analysis of heavy metals. The metals in the present study followed the order Mg>Ca>Zn>Fe>Cu>Mn>Cr>Pb>Ni>Co>Cd. Trace metal concentrations in the soft tissue of the molluscs varied as follows: for Cd: 0.04-5.33, Co: 0.09-0.87, Cr: 2.18-7.59, Cu: 9.54-37.02, Mn: 1.30-8.50, Ni: 0.94-3.21, Pb: 1.16-2.64 and Zn: 68.16-113.64mgkg^-1. Metal concentrations in all the species were below the limits proposed by the World Health Organization, except for Pb and Cd. This baseline study suggests that the levels of toxic metals in M. trapa, T. curta, and B. spinosa should be continuously monitored to assess the fate and effects of these metals in this fragile ecosystem.