Characteristics Of Main Seagrass Beds Microbial Community In Wenchang And The Effects Of Two Kinds Of Land-based Pollutants And Vibrio On The Bacterial Community Of Thalassia Hemprichii

In recent years,seagrass beds in Wenchang,Hainan have been degraded significantly due to land pollution.Microbial community is one of the key factors to ensure the healthy survival of seagrass.However,studies on the effects of land-based pollutants on seagrass microbial communities have not been reported.Therefore,in this study,the microbial community structure of main seagrass beds in Wenchang,Hainan was analyzed by field investigation and laboratory stress test,and the composition of the core bacterial community of Thalassia hemprichii,the dominant species in this area,was further determined.Finally,the effects of feed extract solution,nitrofuran antibiotics and Vibrio harveyi on the bacterial community were studied.The main results are as follows:The ?-biodiversity of rhizosphere bacterial community was the highest in the seagrass beds of Changpi Port,and the root surface and sediment were higher,the leaf surface was lower,and the sea water was the lowest.The bacterial community structure of seagrass in Changpi Harbor was related to seagrass species.The same or similar major microbial communities often exist in the same niche of seagrass in different regions.The core bacteria on the leaf surface of Thalassia hemprichii include 43 genera,such as Propionigenium,Marivita,and Vibrio.The core bacteria in the root surface included 45 genera such as Desulfosarcina;Desulfococcus;and Vibrio.Rhodobacteraceae is an important core bacterial group that maintains the health of seagrass leaf surface.Anaerobic bacteria of Desulfobulbaceae corm family exist on the leaf surface of seagrass,which is caused by a large number of attachments forming an anaerobic environment on the leaf surface.The core bacterial group of the order Chromatiales has important functions such as oxidizing sulfide,removing inorganic nitrogen and reducing Vibrio.The effect of feed extract solution on ?-biodiversity of the bacterial community was not significant,and the microbial community structure of the leaf surface and leaf was significantly changed,but the bacterial community structure of the root surface was not significantly affected.Ammonia salts and phosphate are important environmental factors that promote the proliferation of Bacteroidales and Vibrio,Desulfobulbaceae and Desulfobacteraceae.The Bacteroidales and Vibrio of Thalassia hemprichii leaf responded to and purified land-based pollutants such as ammonium salts,phosphates and organic matter.Sulfate-reducing bacteria of the Desulfobulbaceae and Desulfobacteraceae lead to the increase of sulfides in seagrasses bed environment when the input of land-based organic pollutants increases.The feed extract solution changed the bacterial community structure in the leaves of Thalassia hemprichii,promoted the proliferation of Vibrio bacteria in the leaves,and degraded the nitrate in the feed extract solution by enhancing the nitrate reduction.The effects of feed extract solution on the structure and core bacterial community of the root of Thalassia hemprichii were not significant.Vibrio harveyi was more tolerant to high concentrations of Thalassia hemprichii because Pseudomonas on the leaf surface and root surface inhibited Vibrio harveyi.Nitrofuran antibiotics had little effect on bacterial community structure on leaf surface,leaf inside and root surface.This study determined the composition of core bacterial communities of Thalassia hemprichii,and explained the effects of feed extract solution,nitrofuran antibiotics and Vibrio harveyi on the bacterial communities on the leaf surface,leaf inside and root surface of Thalassia hemprichii,providing a basis for scientific evaluation of the impact of land-based pollution on the microbial community of seagrass.It is of great theoretical significance and practical value to the environmental protection of coastal waters.