| In recent years,industrial pollutants and domestic pollutants have increased,the proportion of heavy metals from human production have significantly increased in offshore area.Microorganisms are regarded as the most important decomposition and initial users of organic matter in the ecosystem,which have play an important role in the material cycle and energy flow of the whole ecosystem.The biological diversity and physiological function of microorganism population are influenced by the changes in natural conditions.Structure and metabolic process of microbial flora are changed,biological diversity and metabolic function of microorganisms in the environment are affected under the adverse conditions,such as high concentration of heavy metals.At the same time,this kind of change to a certain extent can also reflect the level of heavy metal pollution in the environment.In this study,Jinzhou Bay is selected as the research area where has been polluted by heavy metals.Nine stations were choosed show a radil from the near to the distant area in August 2012.The sediments quality and the microbiota,quantity,hydrolytic enzyme activities in it were analysed.The coupling relationship between the changes of microbial community and metabolic function and distribution characteristics of heavy metals in sediments want to be revealed in the heavy metal stress environment.Microorganisms in the process of structural change,metabolic function regulation and the mechanism of resistance to heavy metals will be elucidated.The main conclusions of this study include the following aspects.(1)The content of heavy metals Zn,Cu,Hg and Cd in surface sediments of Jinzhou Bay have obvious spatial distribution.The trend is gradually reduce from southwest coastal area to northeast offshore waters.This indicates that the heavy metal pollution in Jinzhou Bay is dominated by terrigenous input,and 4 kinds of heavy metals have similar input source and distribution characteristics.Most of the content of heavy metal in the sediments more than third types of marine sediment quality standards,which indicates that the Jinzhou Bay area is a region with high heavy metal pollution.The Hakanson potential ecological risk evaluation showed that the strength sequence of heavy metals is Hg>Cd>Cu>Zn.Hg and Cd are the main heavy metal pollution factors in sediments of Jinzhou Bay,which should be strengthened to control.(2)In this study,242 strains of heterotrophic bacteria(17 genus)are obtained.Among them,99 strains(4 genus)of Gram-positive bacteria accounted for 40.91% of the total number of heterotrophic bacteria isolated and 143 strains(15 genus)of Gram-negative bacteria counted up to 59.09%.Bacillus accounted for 24.79%,is the first dominant genu in surface sediments of Jinzhou Bay,followed by Photorhabdus accounted for 19.42%,and the number of Iron bacteria and Acinetobacter are the least,the proportion was 0.41%.In southwest coastal area,the dominant genu are Photobacterium,Bacillus and Clostridium.But the most frequently were Bacillus,Aeromonas,Photobacterium in northeast offshore waters.The composition of dominant species is similar,but there is difference between each other.The number of heterotrophic bacteria in southwest coastal area below the northeast offshore waters,but species diversity is slightly higher,which showed that the heterotrophic bacteria were affected by heavy metals,but also related to other indicators of water and surface sediment.(3)On the whole,hydrolases of heterotrophic bacteria in the same position surface sediments of Jinzhou Bay have different activities under heavy metal stress,and the hydrolases of the same genus in different stations also have different expression.The number of heterotrophic bacteria with low activity was the majority.The activity size of the enzyme is as follows: lipase> protease > amylase > phosphatase.The hydrolase activity of heterotrophic bacteria is higher in southwest coastal area than northeast offshore waters surface sediments of Jinzhou Bay,which similar to the trend of heavy metals.The metabolism of heterotrophic bacteria is changed under the long-term high concentrations of heavy metals pollution in southwest coastal area.Some sensitive bacteria gradually produce adaptability to heavy metals and the increase of enzyme activities could be used as an indicator of heavy metal resistance.There is a significant positive correlation between phosphatase,protease,lipase and the content of heavy metals,can be used as a sensitive index to reflect the heavy metal pollution,which reflect the environmental quality of surface sediments in Jinzhou Bay.(4)The trend of heterotrophic bacteria resist to heavy metals Zn,Cu,Hg,Cd are similar and the resistance is higher in southwest coastal area than northeast offshore waters,which similar to the trend of heavy metals and Hakanson potential ecological risk evaluation.This trend shows that the heavy metal resistance of heterotrophic bacteria is related to the long-term accumulation of heavy metals in the sediments of Jinzhou Bay.The number of heterotrophic bacteria that resist to heavy metals is more in southwest coastal area than northeast offshore waters.In this study,the high concentrations of heavy metals produced a rapid bactericidal effect on heterotrophic bacteria in northeast offshore waters because they have low heavy metal resistance.The heterotrophic bacteria must have a certain resistance to heavy metals in physiological or genetic material in southwest coastal area where heavy metal pollution is a long-term accumulation.In this study,the number of heterotrophic bacteria resistant to Cd and Hg was lower than Zn and Cu,indicating that Hg and Cd had higher ecological toxicity and ecological harm degree,and the control of Hg and Cd pollutants should be strengthened. |
