Microbial ecology might serve as new indicator for the influence of green tide on the coastal water quality: Assessment the bioturbation of Ulva prolifera outbreak on bacterial community in coastal waters

The massive outbreak of Ulva prolifera had brought significant ecological impacts on marine coastal areas. In order to clarify the influence of outbreak of U. prolifera on marine microbial ecosystem, the microbial communities in different stages of blooming were analyzed by high-throughput sequencing. The sequences were clustered into 2979 operational taxonomic units (OTUs), and Shannon estimator varied from 3.241 to 4.892. The OTUs number and Shannon estimator demonstrated that both parameters were higher in samples HY_2-4, QD_2-4, RZ_2-4 than in HY_1, QD_1, RZ_1, indicating that the massive outbreak of U. prolifera caused the increase of microbial community diversity in coastal waters. The outbreak of U. prolifera led to increase in the abundance of some bacteria. According to the network analysis, the differences in hot bacteria in different stages indicated that the outbreak of U. prolifera caused the variation of microbial community. Based on Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis, the abundance of 41 metabolic pathways had changed due to the outbreak of U. prolifera. The microbial community could recover gradually after the disappearance of U. prolifera. The relative abundance of dominant genera Methylophaga, Polaribacter, Marinobacterium, Marivita, Tenacibaculum, Vibrio, Planktomarina, Crocinitomix, Draconibacterium, norank_f_Alteromonadaceae in stage 6 (after the outbreak of U. prolifera) kept the same level as stage 1 (before the outbreak of U. prolifera). These findings suggested that microbial ecology might serve as new indicator for the influence of green tide on the coastal water quality since marine microbial ecosystem could be temporarily bioturbated during the outbreak of the green tide