Cross‐generational effects of climate change on the microbiome of a photosynthetic sponge

Coral reefs are facing increasing pressure from rising seawater temperatures and ocean acidification. Sponges have been proposed as possible winners in the face of climate change, however little is known about the mechanisms underpinning their predicted tolerance. Here we assessed whether microbiome mediated cross‐generational acclimatisation could enable the photosynthetic sponge\ua0Carteriospongia foliascens\ua0to survive under future climate scenarios. To achieve this, we first established the potential for vertical (cross‐generational) transmission of symbionts. Sixty‐four amplicon sequence variants accounting for >90% of the total\ua0C. foliascens\ua0microbial community were present across adult, larval and juvenile life stages, showing that a large proportion of the microbiome is vertically acquired and maintained. When\ua0C. foliascens\ua0were exposed to climate scenarios projected for 2050 and 2100, the host remained visibly unaffected (i.e. no necrosis/bleaching) and the overall microbiome was not significantly different among treatments in adult tissue, the respective larvae or recruits transplanted amongst climate treatments. However, indicator species analysis revealed that parental exposure to future climate scenarios altered the presence and abundance of a small suite of microbial taxa in the recruits, thereby revealing the potential for microbiome mediated cross‐generational acclimatisation through both symbiont shuffling and symbiont switching within a vertically acquired microbiome