Temporal dynamics of the bacterial community structure and functions associated with marine sponges collected off Karah Island, Terengganu, Malaysia

The marine sponge microbiome has been investigated for decades, yet its temporal fluctuation/stability is poorly understood. This study aimed to describe the seasonal dynamics of the bacterial composition and predicted functions associated with two tropical marine sponge species (Aaptos suberitoides and Xestospongia testudinaria) collected off Karah Island, Malaysia, in the three seasons (dry season, pre- and post-monsoon season) using 16S rRNA gene amplicon sequencing and Functional Annotation of Prokaryotic Taxa (FAPROTAX). The bacterial taxonomic structures demonstrated divergences among A. suberitoides, X. testudinaria, and seawater, regardless of seasons. Chloroflexi, Proteobacteria, Cyanobacteria, Actinobacteriota, and Acidobacteriota comprised the core bacterial communities in two marine sponge species throughout the seasons, however, there were differences in bacterial composition between the two marine sponges. In addition, A. suberitoides was enriched with Dadabacteria, Spirochaetota, and Bdellovibrionota, whereas X. testudinaria abundantly harbored Poribacteria, PAUC34f, and Anck6. At the genus level, SAR202 clade and Candidatus Synechococcus spongiarum group dominated marine sponge samples throughout the year. Several genera, such as SAR202 clade, Candidatus Synechococcus spongiarum group, and Entotheonellaceae, were discovered only in marine sponge samples. Spirochaeta and Dadabacteriales displayed higher relative abundances in A. suberitoides, while Poribacteria and PAUC34f were more abundant in X. testudinaria. SAR202 clade was positively correlated with dissolved oxygen (DO), pH, phosphate, and ammonia in A. suberitoides. Likewise, Candidatus Synechococcus spongiarum group was negatively correlated with salinity and nitrate in X. testudinaria. Predicted functions by FAPROTAX annotated the phototrophic-related functions in both marine sponges, which might be attributed to a sponge-specific taxon Candidatus Synechococcus spongiarum group. The functions “predatory or exoparasitic” and “fermentation” were highly detected in A. suberitoides, which might be related to the bacterial genera Bdellovibrio and Spirochaeta, respectively. This study guides a deep understanding of the bacterial community structures associated with tropical marine sponges and their temporal behavior.