Impacts Of Dust On Heterotrophic Bacterial Bioactivity And Community Structure Of Bacteria In China Coastal Marine

Heterotrophic bacteria play significant role in material cycle and energy flow ofMarine ecosystem, occupying a crucial position in marine environment. Heterotrophicbacteria are often limited by nutrients in seawater, such as Nitrogen, Phosphorus andso on, due to their huge population, rapid reproduction, high conversion efficiencyand prompt biological cycle. Dust deposition is one of the sources of marine nutrientsand an important path transporting nutritive material and pollutant from lands tomarine. As a result, it is undeniable that dust deposition is critical to marineheterotrophic bacteria.Effects of Dust deposition on marine ecosystems were reported to be highlyvariable in various oceans. In this study, dust aerosol adding incubation experimentswere conducted at S1station（20.50°N，120.50°E）of South China Sea during March,2013and at H1（37.00°N，124.25°E）and H（236.00°N，123.50°E）station in YellowSea during July,2013, respectively. Process and mechanism of heterotrophic bacterialactivity response to dust in different tropic sea were discussed in this study. Theresults are listed as follows. At S1station in South Sea, dust aerosol facilitatedbacterial biomass increasing as a factor of1.65to control and facilitated bacterialrespiration rate increasing as a factor of2.74to control. At H1and H2station inYellow Sea, dust aerosol facilitated bacterial biomass increasing as a factor of1.78and2.42to control and facilitated bacterial respiration rate increasing as a factor of1.78and2.14to control, respectively. In brief, dust aerosol can obviously promoteheterotrophic bacterial growth and metabolism, signally accelerate bacterialconversion efficiency and apparently enhanced bacteria’s function in marineecosystem, the effect of which is more significant in oligotrophic sea than in eutrophic sea.Dust can combine with heavy metal and toxic organic substance fromatmospheric pollutants in long-term transport. In order to probe into impact ofnutrients from dust on marine heterotrophic bacteria isolatedly, original dustenrichment experiments are conducted at S1and S2station in South China Sea. In thethird days of experiment in S1and S2, the two types of original dust have increasedbacterial biomass and respiration rate tremendously when added alone. And theeffects of small size dust are more conspicuous than big size dust. In the seventh dayof experiment in S1, there is little difference of effects between small size dust andbig size dust. On the basis of adding Nitrogen and Phosphorus, the two types of dusthave restrained heterotrophic bacterial growth and metabolism and the difference ofeffect between small size dust and big size dust is non-significant.Comparison of bacterial community structure before and after dust enrichmentincubation is conducted at S1in South China Sea and H1and H2in Yellow Sea,adopting PCR-DGGE method. The results are as follows. In dust aerosol enrichmentexperiments, variations of bacteria community structure in H1and H2are lesssignificant than in S1. In original dust enrichment experiments, variations of bacteriacommunity structure and diversity resulted from small size dust are more significantthan big size dust. In dust aerosol enrichment experiment and original dust enrichmentexperiment in S1, Alphaproteobacteria and Gammaproteobacteria have turned intodominant species after incubation, while Chloroplast’s dominant place has beendisappeared and the bacteria community switched towards heterothrophy. In dustaerosol enrichment experiment in H1and H2, Chloroplast’s dominant place haveconsolidated, while Proteobacteria’s dominant place has been disappeared andbacteria community switched towards autothrophy.