Not only for corals: exploring the uptake of beneficial microorganisms for corals by sponges.

Microbiome restoration using beneficial microorganisms for corals (BMCs) comprise a promising strategy to help corals cope with anthropogenic stressors. However, there is limited knowledge on the uptake of BMCs by nontarget animals, especially sponges. This study explores whether sponges can acquire BMCs upon direct application and whether inoculations affect sponge health. A 4-week field experiment applying BMCs to Stylissa carteri and Callyspongia crassa assessed three conditions: no inoculation, and BMCs inoculation once and thrice a week. BMC-related strains were naturally present in the seawater and the microbiome of S. carteri. These strains were enriched in response to the inoculation only in the S. carteri microbiome. Microbiomes of both sponges were restructured; sponges were visually healthy and efficiently pumped water at the end of the experiment. These results suggest that sponges can be enriched with BMC-related strains, and that BMC application on nearby corals is unlikely to negatively affect sponge health.