Effects of the tidal dehydration stress on epiphytic bacterial community of the intertidal macroalga <i>Sargassum thunbergii</i>

The adaptive mechanisms of the intertidal macroalgal-epiphytic bacterial symbiotic system to periodic tidal dehydration stress play a crucial role in maintaining coastal ecosystem stability. Although numerous studies have investigated the effects of tidal dehydration on intertidal macroalgae, the impact of dehydration on the epiphytic bacteria has received much less attention. Our investigation revealed that tidal dehydration stress significantly alters both the community structure and metabolic functions of the epiphytic bacteria on <i>Sargassum thunbergii</i>. Notably, dehydration stress selectively enriched stress-tolerant bacterial taxa and induced metabolic reprogramming, particularly in energy, nitrogen, and sulfur cycling pathways. These microbial responses demonstrate not only bacterial stress adaptation strategies but also suggest potential host-mediated regulation within the algal-bacterial symbiotic system. These findings provide novel insights into the ecological adaptability mechanisms of intertidal ecosystems under environmental stress.