The Influence Of Effluent Discharged From A Chemical Industrial Park On Microbial Communities Of The Hangzhou Bay

Owning to the increasing human activities around the Hangzhou Bay, especiallythe rapid development of industrial parks, the bay has been seriously polluted that itspresent nutrition situation was at the highest eutrophic level among China’s coast.However, besides environmental deterioration, the ecological status, especiallymicrobial community, of the Hangzhou Bay has not been concerned yet. Therefore, thisstudy was designed to reveal the microbial communities of the wastewater treatmentsystems in a typical chemical industrial park and its effluent discharge area in theHangzhou Bay, adopting molecular biological technologies. By analyzing therelationship between microbial community and environmental factors, the impact of theinput of the land-sourced industrial pollution on the microbial community of the effluentreceiving area in the bay was explored.Comparing the wastewater treatment systems and the effluent receiving area, thebacterial and archaeal communities of the sediments in the effluent receiving areaowned higher richness and diversity than those in the activated sludge in the wastewatertreatment plants (WWTPs). However, certain pollution resistant genus, i.e. Thauera andTruepera, were detected in both activated sludge and sediments, which probablyindicated the pollutants’ impact on microbial community of the effluent receiving area.The direct effluent connection stimulated the similarity of bacterial communities but notof archaeal communities. In the activated sludge of WWTPs, the abundance of ammoniaoxidizing archaea (AOA) was at extremely low levels, and ammonia oxidizing bacteria(AOB) was the dominant ammonia oxidizer. In the sediments of the effluent receivingarea, AOA and AOB possessed similar abundances. Almost all AOB in both activatedsludge and sediments belonged to Nitrosomonas, and Nitrosopumilus was the mainAOA in the sediments. The impact of land-sourced pollution on the AOB communitywas more evident than that on the AOA community.By comparing the seasonal samples from different sites of the effluent receivingarea, it was found that the microbial community was mainly influenced by seasonalchanges but kept high similarity between samples from different locations. The bacterialcommunities in the sediments were more diversified than that in the waters, however, the diversities of archaeal communities were similar in the sediments and waters. Thedominant bacterial classes in the sediments, Betaproteobacteria andAlphaproteobacteria, exhibited a strong positive correlation with seawater temperatureand a strong negative correlation with COD. The main archaeal class, Marine_Group_I,showed a moderate negative correlation with seawater temperature. Within the currentammonia concentration range (0.1-0.5mg/L), the increase of ammonia concentration inthe seawater probably improved the proportion of ammonia oxidizers in the microbialcommunities, and raised the relative abundance of AOA in the ammonia oxidizers.According to the laboratory simulation experiments, AOA and AOB were found toexhibit higher ammonia oxidizing ability under low (≤0.1mg/L) and high (≥2mg/L)ammonia concentrations, respectively. With the temperature increased from5oC to35oC,the ammonia oxidizing ability of the sediments was enhanced. The improvement ofsalinity motivated AOA to be the dominant ammonia oxidizer in the sediments from theeffluent receiving area in the Hangzhou Bay.