| Yangtze River is the largest river in China. Among all rivers in China, it brings the most amounts of heavy metal pollutions into East China Sea. A nearshore marine mammal,finless porpoise(Neophocaena asiaeorientalis) which was categorized as a Grade ? National Key Protected Animal may be in the risk of heavy metal exposure.To clear understand it, the main content of this study includes:?Firstly,the population from the coast of Lvsi,Jiangsu Provence was made a representative of populations from East China Sea. 16 muscles of finless porpoises and 29 prey species of the finless porpoise and 10 sea water samples were used.Accumulation status of 9 heavy metals in the muscle tissues of finless porpoises, their food sources and sea water was surveyed. Further, the extent of heavy metal accumulation from sea water to organisms was analyzed as well as effects of bio-magnification by heavy metal transportation from preys to the finless porpoise. And then a usual health risk assessment model was applied to evaluate the heavy metal exposure risk on the finless porpoise.? Secondly, given a consideration of the larger outlet of heavy metals from Yangtze River and the chronic exposure of heavy metals to finless porpoises living in East China Sea, they may have accumulated a higher level of heavy metals, at which the potential risk may also exist. Thus, another two populations (Ningbo, Pingtan)were used to reveal the regional difference on heavy metal bioaccumulation.? Thirdly,at present,few obvious evidences had proved the health problem occurred on finless porpoises due to heavy metal exposure. The studies based on associations between genetic polymorphism and accumulation of heavy metals might also provide some information about their potential health risk of sevel certain metals.The results showed:(1) Contents of heavy metals in sea water are lower than the standard which defined the class I quality. For example,0.00213 ?g/ml of As,0.0013 ?g/ml of Cu,0.0004 ?g/ml of Cd and so on were determined in sea water samples. The variance of 9 heavy metals among all species are 5.36±5.58 ?g/g ww,C.V= 1.04 for Mn,6.85±7.73 ?g/g ww,C.V=1.13 for Cu,0.49±0.85 ?g/g ww,C.V=1.73 for Cd,17.48±15.43 ?g/g ww,C.V=0.88 for Zn,0.10±0.11 ?g/g ww C.V=1.08 for Hg,1.66±0.98 ?g/g ww C.V=0.59 for Cr, 3.65±3.46 ?g/g ww, C.V=0.95 for As,0.25±0.19 ?g/g ww,C.V=0.73 for Ni and 0.13±0.11 ?g/g ww,C.V=0.85 for Pb.Totally, Zn with the highest mean concentration was accumulated in bodies of these species, and that followed by Cu and Mn. The relatively high and low values of coefficient of variation were presented for Cd and Cr.(2) The delivering of heavy metals from nature media, such as sea water, into bodies of organisms could be reflected by bioconcentration factors (BCF). Totally,BCF values of Mn, Zn and Cu are much higher to all species than that of other metals.This implies that essential heavy metals are easy to be transferred from sea water into bodies of organisms. On the other hand, higher BCF values were found on non-essential heavy metals, Hg and Pb, only for finless porpoise and several prey species.For example, finless porpoise with the BCF values 1245 and 1348 for Hg and Pb respectively were determined.(3) Although significantly positive correlation was not found between tropic levels and heavy metal concentrations,the positive correlation trend had been found on As whose significant level closed to 0.05. On the other hand,non-essential heavy metals, Hg and Pb, were found with bio-magnification factor (BMF) value >1 on many prey-predator pathways. For Hg, finless porpoise prey on 16 species (55.17%)showed effects of bio-magnification. For Pb, finless porpoise prey on 12 species(41.3%) showed effects of bio-magnification. Although finless porpoise prey on 9 species (31.03%) showed effects of bio-magnification for Zn, more attention should be paid on these heavy metals, Hg, Pb and Zn, which may potentially harmful to organisms.(4) Health risk of heavy metal exposure to finless porpoise living along the coast of Lvsi has been revealed by health risk assessment using RfD-based assessment. The result showed these RQ values were > 1 for almost all heavy metals. Although TRV-based assessment indicated less risk for some heavy metals, the As had indeed presented the risk for health of finless porpoise. Thus, finless porpoises from the waters adjancent Yangtze River had been in the risk of heavy metal exposure but the risk is not huge.(5) For basic accumulation characteristics of trace elements in tissues, Zn, Cu,Mn and Hg were prone to be accumulated in liver (p<0.05), and Cd was prone to be accumulated in liver and kidney (p<0.05). It was showed that significant difference for As, Cu, Hg and Zn in kidney, Cr, Hg, and Mn in liver, As, Cr and Hg in muscle(Kruskal-Wallis test, Dunn's Multiple Comparisons Test, p<0.05). The multiple comparisons (LSD method) for these tissue trace elements revealed more trace element accumulation in tissues of Ningbo and Lvsi populations. Notably, Ningbo population had present an obvious regional difference in accumulation of heavy metals with higher Hg concentrations in three tissues (p<0.05). Hence, in the light of long-term exposure it is necessary to pay more attentions on pollutions of Hg even As which are the non-essentials.(6) MT2 and MT4 exhibited low levels of population genetic diversity. Totally,the numbers of polymorphic sites (S), alleles (h), nucleotide diversity (?) were 6, 7,0.001, respectively for both MT2 and MT4. It was found that only MT4 had two obvious SNPs at loci 344 G/A, 476 A/G. 344 GG/ 476 AA, showing higher frequency(63.64% for Mn, 64.29% for Zn) were higher accumulated Zn and Mn in the liver tissue. Thus, the two SNPs may relate to accumulation of heavy metals. But, their function is still need to be studied in future.Finally, finless porpoises from eastern coastal of China may be in risk. The research conducted an analysis of the marine mammal exposure to heavy metals based on the material which is hard to acquire. This study provided information about bioaccumulation of heavy metals using higher tropic level species for Chinese coastal heavy metal pollution. It also enriched biomonitoring methods, and made a reference for other similar researches, however, more efforts are still needed for environmental health assessment based on finless porpoises using genetic polymorphic biomarkers. |
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