The Bioaccumulation Patterns Of Mercuty And Fatty Acids In Food Chain In Eutrophic Reservoirs

As the most toxic organic mercury,methyl mercury can transfer,bio-accumulate and bio-magnify in food chain,which can lead to a enhance of methyl mercury concentrations in fishe,and ultimately pose a threat to the health of the fish consumer.Ihe nutrient status of reservoirs affects not only the methylation rate of mercury in water environment,but also the accumulation of mercury in food chain.Whereas,most of the water bodies in China are eutrophic,so it is important to explore the mercury accumulation model in the eutrophication reservoir and its influencing factors.Essential fatty acids,as an important part of fatty acids,are not only human health essential nutrients,but also aquatic animals such as fish and other essential nutrients.The eutrophication of reservoirs caused by changes in the structure of algae will inevitably greatly affect the transmission and accumulation of the essential fatty acids in food chain.Secondly,since fatty acids can be conserved after being bioabsorbed,fatty acids are used as important biomarkers for food sources.In this study,we aim to combine the effects of eutrophication on mercury and energy transport in the food chain by combining the accumulation patterns of fatty acids and mercury in the food chain.At the same time,combined with carbon and nitrogen stable isotopes,understanding the accumulation patterns of fatty acids in food chain with nuitrient level.Wujiang River in Guizhou was chosen as the research object,and seven reservoirs of Wujiang River were chosen as the sampling sites,these reservoirs were divided into three categories: eutrophic reservoir(WJD),meso-trophic reservoirs(BHH and HFH),oligo-trophic Reservoirs(HJD,YZD,DF,and SFY).Samples including water,planktons,benthic fauna,and fish collected from reservoirs.In order to understanding the accumulation patterns of mercury and fatty acids in the food chain from different eutrophic reservoirs.The THg,MeHg,carbon,and nitrogen isotopes in the samples were analyzed,and fatty acids of biota samples in WJD and HFH were analyzed.The main conclusions of the research are as follows:(1)The mercury concentrations and the bioaccumulation magnification factors of the organisms varied differently in trophic reservoirs.(2)The concentrations of Hg in food chain had no significant correlation with that in the water,while were negatively correlated with the concentration of Chl-a in the water,and have no significant correlation with the concentrations of TN and TP of the water.In addition,different food chain length and different Biological transmission rate of each reservoir will lead to different mercury concentrations and MeHg% in mercury of fish at the top food chain.(3)The fatty acids compositions of food chain of WJD and HFH were different.The composition of EFAs in different kinds of orangisms were also different.The percentages of n-3PUFAs of plankton and food chain in Hongfeng reservoir were higher than that of Wujiangdu reservoir.The possible reason is that the eutrophication will lead to the lack of n-3 PUFAs in the aquatic food chain,and affect the distribution of fatty acids in living organisms.(4)The accumulation patterns of EFAs and methylmercury in food chain were not the same.Different with methylmercury,the concentrations of EFAs did not increase from the low trophic level to the high trophic level along the food chain.Moreover,the concentration of methylmercury had no significant correlation with the concentrations of total lipids and EFAs.According to the correlation between methyl mercury concentration and EFAs concentrations,we inferred that the methylmercury in food chain of WJD and HFH came from the bacteria food sources,and had no significant relationships with algae and terrestrial food sources.