Spatial-temporal dynamics of bacterioplankton communities in the breeding area of large yellow croaker Larimichthys crocea in Sansha Bay,China

As an important spawning ground for large yellow croaker Larimichthys crocea,Sansha Bay,South China Sea has been a research hotspot.However,studies on the influence of the bacterioplankton community and assessments of its seasonal succession of bacterioplankton in different sea areas in Sansha Bay are still limited.To address the issue,we use 16S rRNA gene amplicon sequencing and functional prediction to investigate the spatial-temporal dynamics of the bacterioplankton community in three distinct areas,i.e.,Breeding Area(BA),Yantian Harbor(YH),and Bay Margin(BM)of Sansha Bay.Results show that the structure of the bacterioplankton community in Sansha Bay had a significant seasonal succession.Moreover,the representative zero-radius Operation Taxon Units in different seasons were significantly different among the three selected sea areas.Specifically,during the breeding season,bacterioplankton communities in BA were characterized by compound-degrading bacteria,such as Rhodococcus and Owenweeksia,while in YH and BM,animal parasites or symbionts such as Vibrio and Arcobacter were dominant.Furthermore,the redundancy analysis and Spearman correlation analysis further explained that water temperature,dissolved oxygen,and ammonia nitrogen were the main environmental factors responsible for the difference.In addition,the bioindicator functions screened by Functional Annotation of Prokaryotic Taxa and random forest machine learning mainly relied on compound degradation,nitrite oxidation,and photoheterotrophy.The compound-degradationcorresponded bacterioplankton genera such as Rhodococcus had relatively higher abundance in BM,while Nitrospina corresponding to nitrite oxidation tended to be abundant in YH and BA.Based on the spatial and temporal variation in the composition and function of bacterioplankton,our findings provide a basis for understanding the theory of bacterioplankton community structure in the inner-bay habitat of the large yellow croaker in Sansha Bay.