Abundance, Community Structure And Environmental Factors Of Nitrifying Microorganisms In The Offshore Near The Crowded District With Aquacultre Plants And Food Manufactural Factories

Microorganisms mediate the marine nitrogen cycle,regulating the availability of nutrients,primary productivity,and greenhouse gas production and consumption.Marine microbial ecology is an important part of marine ecosystems.In recent decades,due to the rapid development of aquaculture and food processing industry,the eutrophication of coastal waters has been aggravated by the rapid development of aquaculture and food processing industries,which has a certain impact on the microbial ecology of the western Guangdong waters.The investigation of microbial ecology in the waters of this region is of great practical significance for understanding the environmental conditions and formulating environmental protection and countermeasures.Nitrification,which consists of the ammonia oxidation process driven by ammonia-oxidizing archaea(AOA)and ammonia-oxidizing bacteria(AOB)and the nitrite oxidation process performed by nitrite-oxidizing bacteria(NOB),is a key central link in the marine nitrogen cycle.Ammonia-oxidizing microorganisms are widely distributed in nature,and their relative abundance,biodiversity,and relative contribution to overall nitrification vary from environment to environment;NOB has been neglected when it was discovered that NOB has many other ecological functions besides oxidizing nitrite.At present,the spatial and temporal distribution characteristics of nitrifying microorganisms in tropical offshore areas are still not well understood.Therefore,it is scientifically meaningful to study the temporal and spatial distribution of AOA,AOB and NOB in the same region.Abundance,diversity,community structure and environmental factors of ammonia oxidizers and nitrite oxidizers,and environmental factors were firstly synthesized by RT-PCR and amplicon high-throughput sequencing from the Zhanjiang Bay to the northwestern of the South China Sea,which was based on the ammonia monooxygenase(AMO)gene(amoA)and the nitrite oxidoreductase(NXR)gene(nxrB).we draw the following conclusions:1.In winter the abundance of AOB is significantly higher than other seasons in Zhanjiang Bay,the abundance of AOA was stable at 10~5 copies.The abundance of Nitrospira was significantly higher than Nitrospina in Zhanjiang Bay.From Zhanjiang Bay mouth to the continental shelf of western Guangdong,the abundance of AOA is increasing in the horizontal direction,the abundance of AOB was stable at 10~6 copies.The abundance of Nitrospira and Nitrospina is increasing from the near shore to the middle of the shelf,then remains stable.In the vertical direction of the northwestern of the South China Sea,AOA increases with the increasing sampling depth,reaching the maximum abundance in the middle of the euphotic(100m),tending to be stable downward,AOB is stable at the 10~5 copies.The largest abundance of Nitrospira is on the surface,and decreases with the increasing sampling depth.It reaches the minimum of the abundance in the middle of the euphotic(100m)and remains stable.Nitrospina has no difference in the near surface layer(0-50m).As the sampling depth increases,it continues to increase.2.The lowest biodiversity of AOA and AOB,Nitrospira and Nitrospina in Huguang Maar Lake,while shows the largest biodiversity in Zhanjiang Bay.There are significant differences in the community composition of ammonia-oxidizing microorganisms in different habitats:the main genus of AOA in Zhanjiang Bay and Huguang Maar Lake is Nitrosopumilus,the main genus of AOB in the waters of Zhanjiang Bay is Nitrosomonas,while the dominant genus of AOB in the sediments of Zhanjiang Bay and Huguang Maar Lake is Nitrosospira.The composition of Nitrospira and Nitrospina in different habitats is also significantly different,Nitrospira is ubiquitous in all habitats,Nitrospina is almost exclusively found in saltwater habitats.3.Temperature(P<0.01),salinity(P<0.05),pH(P<0.001)and nitrate concentration(P<0.05)significantly affect the community structure of AOA in Zhanjiang Bay and Huguang Maar Lake.The community structure of AOB was also affected by temperature(P<0.05),salinity(P<0.05)and nitrate concentration(P<0.001).The community structure of Nitrospira was affected by temperature(P<0.001),salinity(P<0.05),pH(P<0.001)and dissolved oxygen content(P<0.01).The community structure of Nitrospina was only affected by temperature(P<0.05)and dissolved oxygen(P<0.01).Temperature and dissolved oxygen regulate the abundance of ammonia-oxidizing microorganisms in Zhanjiang Bay.The abundance of Nitrospira and Nitrospina is affected by the concentration of ammonium,nitrite and nitrate,in addition to temperature and dissolved oxygen.