Seasonal heavy metals accumulation in the soft tissue of <i>Anadara granosa</i> mollusc form Tanjung Balai, Indonesia

Abstract

A problem of food safety may rise in benthic estuary organisms such as the bivalve mollusc of Anadara granosa, as dangerous metals in environment may accumulate in their soft tissue. Fluctuation of accumulation may also happen, as there are factors that influence the amount of pollutants in water environment. This research aimed to analyze the seasonal pattern (Indonesian east, intermediate, and west monsoon season) of heavy metals (Cr, Co, As, Cd, Hg and Pb) accumulation factor in the soft tissue A. granosa and evaluate the use of mollusc as bio-indicator in metals pollution. The study had been done on the estuary of Tanjung Balai, North Sumatra, Indonesia. Heavy metal from water, sediment, and soft tissue of A. granosa were extracted by microwave digestion and analyzed by ICP-MS (Inductively Coupled Plasma-Mass Spectrometer). Result of the study showed that the heavy metals accumulation in the soft tissue of A. granosa was as follow Cd > As > Hg > Pb > Cr > Co and between 0.01–0.31 mg/kg. The concentration may consider as safe, which is below the maximum allowable limits for marine products. Meanwhile, a significant (P < 0.05) heavy metals contamination was detected higher in the beginning east monsoon season. Thus, temporal variation should be considered in food safety monitoring program on fisheries products, which usually only collected once per year. Moreover, BWAF (bio-water accumulation factor) was detected significantly (P < 0.05) higher than BSAF (bio-sediment accumulation factor). The results also showed only Cr and Pb had a significant relation (P < 0.05) between their accumulation in environment and in the mollusc. Therefore, environmental parameters need to take into account when using bivalves as indicator of heavy metal pollution since seasonality could affect the absorption of heavy metals.