Purpose To study the structure of the epiphytic bacterial community of the male and female Porphyra haitanensis, in order to explore the similarities and differences of epiphytic bacterial community structure between dioecious macroalgae. Methods Collection of male and female Porphyra haitanensis from the intertidal zone of Niushan Island, Fujian, China. Epiphytic bacteria were collected and studied, and the community composition and diversity of epiphytic bacteria were explored using high-throughput sequencing technology. Results There was no significant difference between male and female Porphyra haitanensis on α-diversity and β-diversity. Proteobacteria and Bacteroidetes were the core microbiota in male and female Porphyra haitanensis. Bacteria from the Maribacter (male 14.87%, female 1.66%) and the Tenacibaculum (male 1.44%, female 25.78%) were the most indicative epiphytic bacterial taxa on male and female Porphyra haitanensis. Conclusions Sex differences have some influence on the construction of epiphytic bacterial communities in Porphyra haitanensis, but they are not the decisive factors affecting the construction of epiphytic bacterial communities in Porphyra haitanensis.

The epiphytic bacteria are the most abundant microorganisms on marine macroalga. However, there are few studies on the distribution of these epiphytic bacteria on male and female Sargassum thunbergii. In this study, the composition and diversity of epiphytic bacterial communities on male and female S. thunbergii were investigated by using the traditional culture-based method and 16S rDNA high-throughput sequencing. The results showed that the dominant bacterial phyla and genera were the same on both male and female S. thunbergii. However, there were significant differences in the relative abundance of epiphytic bacteria at the genus level. Furthermore, male and female S. thunbergii had their own indicative species and specific bacteria. In addition, the predicted functions of the epiphytic bacteria mainly differed in transport and metabolism, environmental adaptation and spore development. This study enriches the baseline knowledge of epiphytic bacteria related to dioecious algae and paves the way for further studies of the relationships between epiphytic microbial communities and the sex of algae.