Biomagnification Of Heavy Metals In Common Fish From Mangrove Areas Of China

With the rapid development of science technology and society,heavy metal pollution has brought many harms to human beings,which causes extensive concern, and thus the study of heavy metal pollution has become one of the hot researching spots of environmental science and biology.In combination of pollution ecology,the technique of stable isotope was introduced to the study of mangrove ecosystem.Based on the comparison of different methods of digestion,the characteristics of conctent of eight heavy metals,including Cu,Zn,Pb,Cd,Cr,As,Hg and MeHg,and their biomagnification in food web(chain),have been studied in bodies of primarily economic shrimps and fishes in three mangrove forests.This will provide scientific basis for the assessment of environment and food safety in southeast costal areas of China.Here are the main results:1 The content of heavy metals in fishes of main mangrove forests are in the order of Zn＞Cr＞Cu＞As＞Hg＞Pb＞Cd＞MeHg.There were consistent geographic characterizations of heavy metal content in Sillago sihama,Siganus oramin,and Therapon theraps,with the order of Fugong＞Da Guansha＞Dong Zhagang of Sillago sihama,and Da Guansha＞Dong Zhagang of Siganus oramin and Therapon theraps,respectively.However,the distribution of heavy metal content in Inegocia guttata within the three districts did not show any similar regularity Besides the effects of their own metabolism,heavy metal contents in fishes were also affected by their habitats significantly.2 The content of heavy metals in fishes of different areas changed irregularly with water layers in which they inhabit.But in terms of feeding habits,Cu content were in the order of herbivorous＞omnivorous＞carnivorous;this indicated the existence of biodilution;whereas,As,Hg content were in the order of carnivorous＞omnivorous＞herbivorous and this showed biomagnification.Correlation regression analysis showed that there were significantly positive relationships between As and Hg in Dong Zhaigang,Cu and Pb in Da Guansha,Cr and As in Fugong;and that there were significantly negative relationships between Pb and length in Dong Zhaizhang,Zn and weight in Da Guangsha,Cr and length in Fugong.3 In Fugong,Cr,Pb,Hg contents were all in the order of bids＞fishes＞shrimps; MeHg was in the order of fishes＞birds＞shrimps;Cu content was in the order of birds＞shrimps＞fishes;Zn content was in the order of shrimps＞birds＞fishes;As content was in the order of shrimps＞fishes＞birds;Cd content was in the order of fishes＞shrimps＞birds.And there were three patterns of the heavy metal distributions in Sillago sihama and the other four types of fish,which are in the order of winter＞summer with Cu,Zn,As,Hg,Cd,summer＞winter with Cr,and irregular changes with Pb,MeHg.4 Fishes' quality was evaluated by using of national standards coupled with bio-mass index method and results showed that:the quality indexes of Cu,Zn,Cd,Pb, MeHg were below 1,but Cr,As,Hg of some fish were above 1,this indicated the corresponding pollution,thus some agents ought to attach importance to this issue.5δ¹³C of fish from Fugong had the smallest change extent,which showed that fish studied from this region had the similar food sources;δ¹⁵N of fish from Da Guansha had the smallest change extent,which showed that fish studied from this region had the similar trophic position in food chains.Correlation analysis showed that there were significantly negative correlation between Cu andδ¹⁵N in the three regions and thus there existed biodilution;however there were much significantly positive correlation between Hg andδ¹⁵N and this showed the effect of biomagnification;there was also positive relationship between As andδ¹⁵N.These results were in accord with that from feeding habitat analysis.