Deciphering the response mechanism of microorganisms to green tide outbreaks: Diversity, assembly processes, and co-occurrence patterns

Green tide, a widespread coastal water environmental issue, significantly impacts the ecology of nearshore microorganisms. Despite extensive studies on green tides, the responses of microbial communities and their assembly mechanisms during the development of green tide remain poorly understood. To elucidate these responses and underlying mechanisms, we conducted a comprehensive study examining the diversity, composition, and ecological dynamics of prokaryotic and microeukaryotic communities at various phases of green tide events by integrating high-throughput sequencing. The results revealed that deterministic processes predominated prokaryotic community assembly during green tide events, transitioning to stochastic processes in the post-bloom phase, while the assembly of microeukaryotic communities was consistently driven by deterministic processes at all phases. Co-occurrence network analysis indicated that green tide outbreaks reduced the connectivity and modularity of microbial networks, thereby weakening their overall stability. Functional predictions suggested that green tides may suppress nitrogen fixation while enhancing nitrification and denitrification, potentially altering nitrogen availability in coastal ecosystems. Moreover, we observed an enhancement of the dddL gene, which may contribute to an increased production of dimethyl sulfide (DMS), thereby impacting the sulfur cycle in the atmosphere. Overall, this study provides a foundational microbial dataset and novel insights into the dynamics of microbial networks during green tide events. These findings offer a better understanding of the microbial community's response to green tides and their potential impacts on biogeochemical cycles in coastal ecosystems.