The Bioaccumulation Of Mercury In The Fish-heron Food Chain At The Sanjiang Plain

Wetlands are just like a pool of mercury(Hg),which could make a large amount of mercury accumulate and convert to methylmercury(MeHg)with stronger toxicity.It is necessary to study the distribution and ecological effect of Hg in different trophic levels of the food chain in the wetland ecosystem,moreover,which is helpful for the proper evaluation of ecological risk of mercury pollution in wetland,and the protection of endangered species.Wetland birds is one important part of the wetland ecosystem,which exposures to mercury is mainly due to the consumption of fish enriched mercury.Meanwhile,wetland birds located at the top of the food chain,so they had highest degree of enrichment of mercury in wetland ecosystem.Sanjiang Plain,Chinese largest swamp distribution area,located at eastern Heilongjiang Province,which had abundant water resources and species in this area.Carrying out the study of the bioaccumulation of Hg in the fish-heron food chain at the Sanjiang Plain,can not only help to monitor the Hg pollution status of wetland,but also protect the biodiversity of wetland.The research samples in Sanjiang National Nature Reserve and Xingkai Lake National Nature Reserve were collected,respectively in June 2013 and May 2015.The samples including feathers,tissue,eggshell and guano of Grey heron and Great egret,fish,insects,crustaceans,plant and soil.For these sample,we analyzed the Hg content and the ratio of isotope C and N,studied the Hg and MeHg bioaccumulation effect,and explored the the transfer and accumulation of mercury and diet structure in the fish-heron food chain of wetland.Results as following:(1)The total Hg(T-Hg)and MeHg concentration in the food of Grey heron juveniles is higher than Great egret juveniles,so the T-Hg and MeHg concentration in different tissues(muscle,liver,kidney and brain)of Grey heron juveniles is higher than Great egret juveniles.(2)The Hg content in different tissues of Grey heron juveniles and Great egret juveniles is different,and the order of the T-Hg and MeHg concentration was: liver > kidney > muscle > brain.(3)The Hg content in feathers of Grey heron is different,and the order of the T-Hg concentration was: Grey heron adult feathers > Grey heron juveniles feathers.(4)The Hg content in feathers,eggshell and guano of Grey heron is different and the order of the T-Hg concentration was: feather > guano > eggshell.(5)The Hg content of fish with different diet is different and the order of the T-Hg concentration in fish with different feeding habits in Sanjiang Nature Reserve was: carnivorous fish > omnivorous fish > herbivorous fish;The order of the T-Hg concentration in fish with different feeding habits in Xingkai Lake Nature Reserve was: carnivorous fish > omnivorous fish > plankton-feeding fish;(6)The order of the T-Hg concentration of organisms in different trophic levels at Sanjiang wetland ecosystem was: waterbirds(Grey Heron,Great Egret)> carnivorous fish(Longnose Gudgeon)> omnivorous fish(Crucian Carp)> herbivorous fish(Grass Carp)> aquatic insects(Predacious Diving Beetle)> aquatic plant(Reed);The order of the T-Hg concentration of organisms in different trophic levels at Xingkai Lake wetland ecosystem was: waterbirds(Grey Heron)> carnivorous fish(Amur pike,Amur sleeper and Catfish)> omnivorous fish(Ryu Keun fish,Yellow cartfish,Oriental weatherfish,Crucian Carp,Stone moroko)> planktonfeeding fish(Bighead carp)> aquatic insects(Predacious Diving Beetle)> aquatic plant(Reed etc.);(7)The higher T-Hg concentration of organism is,the higher MeHg concentration and proportion of tissue is.With the increase of trophic level,the amplification of Hg content increase gradually;(8)With the increase of trophic level,the ratio of food intake between adjacent trophic levels decreased gradually,while the ratio of food intake between interval trophic levels increase significantly.Based on the study of Hg bioaccumulation in different in the fish-heron food chain at the Sanjiang Plain,we could understand the Hg enrichment status of organisms in different trophic level,provide reasonable and scientific data support for the protection of the ecosystem at the Sanjiang Plain,and promote the study of Hg pollution in the wetland.