Giant kelp microbiome altered in the presence of epiphytes

Characterizing patterns in the microbial communities associated with canopy-forming kelps is critical to understanding the mechanisms shaping macroalgal microbiomes. Using 16S rRNA gene sequencing, we characterized bacterial and archaeal communities associated with giant kelp in the Santa Barbara Channel. Our results indicate that kelp-associated microbial communities are altered in the presence of epiphytic bryozoans and reflect changes previously observed in other studies of stressed macroalgae. This observation is indicative of patterns of microbiome disruption (dysbiosis) and opportunistic pathogenesis that may have implications for the health and productivity of foundational species of macroalgae. Our study highlights new patterns in host-microbiome associations and reveals the importance of considering host source and condition when investigating the dynamics of macroalgal microbiomes.