Response Of Macrobenthos On Human Activities And The Ecological Restoration In East Shoal Of Chongming Island

East shoal of Chongming island,the largest tidal wetland in Yangtze estuary,is one of the ecological sensitive areas in the world.It is not only transit station,wintering grounds of migratory birds and essential habitat of endangered birds,but also the spawning grounds and migration channels of aquatic animals.East shoal of Chongming island plays an important role in conservation of biodiversity and utilization of wetland resources,thus a national bird reserve was established in the east shoal of Chongming island and it was accepted as the member of east Asia-Australia wader reserve network.Furthermore,It is the International Grade A2 Grade Wetland Ecosystem Type and listed into the list of chinese and international important wetland.The environmental condition about it has aroused great attention from domestic and overseas scholars.Due to the particularity of location,its ecological environment is extremely susceptible to typhoon,reclamation,pollution and other natural and human activities.Although east shoal of Chongming island has established nature reserves,it is still affected by human activities such as grazing,land reclamations.However,the influence of human activities on species diversity and habitat condition is unclear.Thus,it was studied to explore the effects of human activities on the macrobenthic community structure and heavy metal-enrichment caused by human activities on the dominant species of macrobenthos.What's more,it explored whether the artificial oyster reefs has feasibility on ecological restoration on east shoal of Chongming island.The results are as follows:1.Effects of human activities on the community structure of macrobenthos in east shoal of Chongming islandA quantitative sampling survey on macrobenthos was conducted in the intertidal zone of east shoal of Chongming island in April(spring),July(summer),October(autumn)and December(winter)2016.Combined with the present situation,five sample sites were set up(S1-S5).S1 site located in a region without interference of human activities;S2 area is mainly affected by grazing and the S3-S5 area is the remaining tidal flat.The results showed that there was no significant difference in the number of species in each region.The trend of density was S2>S1>S3>S4>S5,and the the trend of biomass present S2>S1>S3>S4>S5.Margalef species richness index d,Pielou species evenness index J and Shannon-Wiener species diversity index H' were significantly different in each site.Compared with the historical data of 2012(before land reclamation),the number of species remained invariant in S1,S2 and S3 sites,while decreased in S4 and S5.The biomass incerased in S1 and S2,while decreased in S3-S5.The abundance of macrobenthos increased in S1,while decreased in S2-S5,The above results showed that the undisturbed natural tidal flat had the ability of self-recovery,grazing had a certain effect on the biomass of macrobenthos;To some extent,the number of species,density and biomass of macrobenthos were influenced by reclamation.The general trend of macrobenthic secondary productivity in east shoal of Chongming island was S1>S2>S3>S4>S5.Compared with the historical data,the secondary productivity of east shoal of Chongming island shows a declining trend,and the descending rate is S5>S4>S3>S2>S1.The functional group of macrobenthos in east shoal of Chongming island are mainly composed of Planktophagous(PI),Phytophagoue(Ph),Carnivorous(C),Omnivorous(O)and Detritivorous group(D).The functional groups are relatively homogeneous in S1,S2 and S3 sites,while asymmetrical in S4 and S5 sites.The above results showed that the grazing and reclamation reduced the secondary productivity of macrobenthos in east shoal of Chongming island.And reclamation had a certain influence on the structure of macrobenthos.In this study,the habitat health condition of the intertidal zone in east shoal of Chongming island was evaluated by ABC curve,H',taxonomic diversity index,BOPA index,marine benthic index(AMBI)and multivariate marine benthic index(M-AMBI).Taxonomic diversity index and BOPA index indicated that the condition of each site was high.H' and ABC curve evaluation results showed that the condition of S1 site was high;S2,S3 and S5 site were good and S4 site was general.The results of AMBI evaluation indicated that S1-S4 was in good condition and the S5 site was high.The results of M-AMBI evaluation showed that the conditions of S1,S3 and S5 were high,S2 and S4 were good.In summary,grazing and the reclamation project had a certain effect on the community structure of macrobenthos,and had caused some disturbance to the habitat in east shoal of Chongming island.2.Effects of cadmium on lipid metabolism in Chiromantes dehaaniIn order to investigate the effects of heavy metal enrichment,which were caused by reclamation,on macrobenthic species.In this study,the effects of cadmium on lipid metabolism were investigated in Chiromantes dehaani,the common dominant species of macrobenthos in the Yangtze estuary.Crabs were randomly exposed to four treatment groups(0.05,0.1,0.5 and 1mg/L)and a control group,after which the structure and lipid contents of gill and were measured.Also the substance contents and the activities,gene expression of the enzyme in lipid digestion,synthesis and transport metabolism.Obvious changes in gill were found that lamella thickened,hemocytes increased in the blood cavity and sub-chitin sapce shrinked in treatment group.Changes in ultrastructure of hepatopancreas were obvered as mitochondrial membrane began to break,the number of mitochondrial cristae decreased and the length became shorter,even disappeared;the nuclear membrane disintegrated,nucleolus extended,nuclear membrane deformed;the microvilli thinned and showed partly falling;Number of P/Ca granules decreased,even disappeared;And many vacuoles formed between the basement membrane and columnar epithelium.The results showed that the lipid contents in the hepatopancreas and ovary decreased after prolonged exposure to cadmium compared to the control.The contents of serum triglyceride(TG),total cholesterol(TCh)presented upgrade firstly than descending latter tendency.The lipase activity decreased while the activities of fatty acid synthase(FAS)and acetyl coenzyme A(ACC)in the hepatopancreas increased on day 7 but decreased on days 14 and 21.Moreover,the change in non-esterified fatty acid level and ACC in the ovary were similar to FAS.The level of low-density lipoprotein increased in the exposed crabs compared to the control group while the level of high-density lipoprotein and the activity of lipoprotein lipase decreased.And the gene expression of FABP and FAS presented increased firstly and descending latter.These observations suggest that cadmium decreases the lipid content by weakening the ability of digestion,transportation and synthase of lipid.3.Investigation on ecological restoration effect of artificial oyster reef in Yangtze estuaryIn order to explore the effect of artificial restoration(proliferation and release of oysters),the community structure of macrobenthos in the artificial oyster reef of Yangtze estuary was tracked in April 2016(before release)and September 2016(after release).The results showed that S2 and N2,the low salinity regions,had no oysters,barnacles and macrobenthos.The abundance and biomass of oysters and barnacles in the S5 and S8 samples were increased.The abundance of oysters basically unchanged in the N6 and N9,while the biomass increased;Abundance and biomass of barnacle in the N9 site increased,while decreasing in the N6.These results showed that the number,abundance,biomass and diversity index of macrobenthos increased after the enhancement and releasing.The results of DCA suggested that the abundance of barnacles was positively correlated with the number of macrobenthos species,biodiversity index(H',J,d).What's more,there was a positive correlation between oyster abundance and species number.The results showed that the community structure of macrobenthos can be improved after the enhancement and releasing.The habitat condition of artificial oyster reefs were evaluated by ABC curve,H',taxonomy diversity index,AMBI and M-AMBI.The results showed that the condition of each site can be improved after the enhancement and releasing.The above results indicate that the enhancement and releaseing of oysters had a certain effect on the improvment of the community structure of macrobenthos in the middle and high salinity areas.