Transmission And Accumulation Of Heavy Metal In Chlorella-Ruditapes Philippinarum Food Chain

With the rapid development of scientific technology and society, heavy metal pollution has threatened marine environment, especieally aquaculture environment, which were taken seriously. Its pollution has become one of the hot researching spots of environmental science and biology. Heavy metals will be biomagnified and transferred into seafood, especially along with seafood chains of the shellfish, which will threaten oure survival, life and health badly. Thus, the study of transmission and accumulation of heavy metals in the algae-shellfish food chain has important theoretical and practical significance. In this paper, the transmission and accumulation of copper, lead and cadmium in the Chlorella-Ruditapes philippinarum food chain was studied, and the main conclusions were as follows:1. The experiment, Ruditapes philippinarum's accumulation of heavy metal in seawater was carried out in law-hydrostatic method. The condition of seawater was suitable for the experiment, with The salinity of 28.5-29.0‰, pH of 8.1-8.3. The concentration of heavy metals (Cu²⁺, Pb²⁺and Cd²⁺) in the seawater was set for the three series of 10μg/L, 50μg/L, 100μg/L. The shell length of Ruditapes philippinarum with the strong and same scale was choosed, which was 3.0-3.6 cm in length, and 6.0-7.8 g in weight. The seashell was sampled for detecting heavy metal with GF-AAS in 1 d, 3 d, 5 d, 10 d, 15 d, 20 d, 25 d and 30 d. The test results showed that The bioconcentration factors (BCF) of Cu, Pb, Cd by Ruditapes philippinarum were 105-268, 185-690 and 26-85 expectively, and its bioconcentration ability and speed was Pb>Cu>Cd; as the concentration of heavy metal in seawater increased, the residuce of heavy metals in shellfish showed higher, but the BCF decreased. 2. Stress and accumulation of heavy metal in Chlorella was studied, and the Chlorella were cultured under the seawater condition with 20±1℃in water temperature, 31-32.5‰in salinity and 4000 lx in light intensity. In the toxic experiment of heavy metals in the seawater, its concentrations were set for 10μg/L, 50μg/L and 100μg/L. The results showed that, the suppression to the Chlorella growth became stronger with the concentration of heavy metal ion higher. The toxicity of heavy metals on Chlorella was Cd²⁺> Pb²⁺>Cu²⁺. Chlorella had strong accumulation ability of Cu, Pb, Cd, and its BCF in state of balance were 1626-3161,3198-7799 and 9313-5438, respectively. with the concentrations of heavy metals in seawater increasing, the accumulation increased, but the BCF decreased.3. Accumulation and transmission of heavy metal Cu, Pb, Cd in Chlorella-Ruditapes philippinarum food chain was simulated under controlled conditions. BCF of Cu, Pb, Cd in Chlorella and Ruditapes philippinarum were determined, followed by BMF of Cu, Pb, Cd in Chlorella-Ruditapes philippinarum food chain. In the system of heavy metal-seawater-Chlorella-Ruditapes philippinarum, Ruditapes philippinarum had a stronger ability of biological enrichment of Cu, Pb and Cd. The contents of heavy metals in Ruditapes philippinarum inceased significantly in the cultured time. The BCF in Ruditapes philippinarum from food chain were 364-821, 1089-936 and 245-736. The BCF of different heavy metal was Pb>Cu>Cd. The BCFs through Chlorella were much larger than through Ruditapes philippinarum and the BMF(<1)showed that there was no obvious biomagnification effects on Chlorella-Ruditapes philippinarum food chainThe study will provide a theoretical base for studying the ecotoxicology of heavy metals on shellfish, and provide a scientific support for developing the limits of hazardous substances in aquatic products.