Study On The Response Characteristics Of Marine Biofilm To Copper Stress

The coastal ecological environment of many countries is threatened by heavy metal pollution,ocean acidification(OA)and seawater eutrophication,which affects the health of marine ecosystem and dampens the sustainable development of marine blue economy.And the efficient monitoring is an important strategy in solving such problem.Given that potential application of marine biofilm in environment monitoring field,we conducted experiments to test the response of marine biofilm bacterial community to the stress of heavy metal copper ion under the condition of ocean acidification or seawater eutrophication were studied using biofilm from the South China Sea through laboratory microcosm experiment and microbial community analysis technology.(1)Under acidification condition,acidification treatment had a significant effect on the relative abundance of most genera in biofilm bacterial communities,for example,compared to pH 8.2,pH 7.7 treatments,pH 7.4 treatment reduced the relative abundances of Marinobacter,Aquibacter and Halomonas,but increased the relative abundances of Alterythrobacter,Erythrobacter,Roseovarius and Ruegeria.However,copper stress had no significant effect on the relative abundances of most genera.The key species of pH 8.2,pH 7.7 and pH 7.4 were Granulosicoccus or Sva0996_marine_group,Coxiella and Leuctotrix,respectively.There was no significant effect on the richness of marine biofilm bacterial community(ACE and Chaol)of each treatment.The pH and pH × Cu interaction had significant effect on the diversity of marine bacterial community(P<0.05).The community structure at pH 7.4 was significantly different from that at pH 7.7 and pH 8.2.The ecological network of bacterial community under three pH conditions showed that the reduction of pH to 7.4 led to the simplification and recombination of bacterial community,while the network modularity of pH 8.2 and pH 7.7 treatment was better and more stable than that of pH 7.4 treatment.The functional prediction showed that the relative abundance of functional genes related to genetic information processing in 0.08 mg/L copper stress was higher than that in 0.02 mg/L copper stress under pH 8.2 treatment.At pH 7.7 treatment,0.08 mg/L copper stress impaired the nucleotide metabolism and functional genes related to the organic systems in the bacterial community.At pH 7.4 treatment,0.02 mg/L and 0.08 mg/L copper stress reduced the relative abundance of the functional genes related to genetic information processing and metabolism in the community.(2)Under eutrophication condition,the biofilm bacterial community compositon of each treatment was different.The relative abundances of Chloroflexi and Acidobacteria in SRH and SCC treatments were significantly higher than those in other treatments,while the relative abundances of Planctomycetes in SRH and SCC treatments were lower than those in other treatments.Eutrophication,copper and eutrophication × copper interaction had significant effects on the relative abundance of most genera(P<0.05).Ilumatobacter and Lactobacillus were the dominant species in SCC and SRH.The key species in the low,medium and high eutrophication groups were Lachnospiraceae_NK4A136_group,Sva0081_sediment_group and Staphylococcus,respectively.The ACE and Chaol indexes of control treatment group SCC,and high concentration eutrophication and high concentration copper stress treatment group SRH were significantly different from those in other treatment groups(P<0.05).Except for the significant effect of Cu2+on Simpson index,eutrophication,copper and eutrophication × copper had almost no significant effect on the diversity of marine bacterial community.The changes of bacterial community structure in SCC and SRH treatments were significantly different from those in the other seven treatments.The ecological network of low,medium and high eutrophication treatments showed that the R2 of low eutrophication treatmentwas 0.678,which lower than that of medium and high eutrophication treatments.The number of network modules of high eutrophication treatment was 11,which lower than that in other treatments.The functional prediction results showed that the relative abundance of carbohydrate metabolism,energy metabolism,glycan biosynthesis and metabolism,biosynthesis of other secondary metabolites and other types of genetic information processing such as translation,replication and repair,folding,sorting and degradation in the treatment of SRH and SCC were significantly higher than that of other treatment groups.In the experiment,the marine biofilm was used to reveal the response characteristics of microbial community to heavy metal copper ion ctress under acidification or eutrophication from the bacterial community level.The experimental results provide valuable references for the marine biofilm in marine ecological environment monitoring in community level.