Not Only in Corals: Beneficial Microorganisms for Corals can also Be Enriched in Sponges

Abstract Microbiome restoration and rehabilitation using beneficial microorganisms for corals (BMCs) comprise a promising strategy to help corals cope with anthropogenic stressors. However, there is a lack of knowledge on BMC uptake in situ and the potential interactions with nontarget animals, especially filter-feeders such as sponges. Herein, this study explores whether sponges can acquire BMCs upon direct application and whether these probiotic inoculations affect sponge health. A 4-week in situ experiment applying BMCs to sponges Stylissa carteri and Callyspongia crassa assesses three conditions: no BMC inoculation (control), and BMC inoculation once and thrice a week. BMCs are naturally available in the seawater and as members of the native microbiome only of S. carteri. The natural presence of BMCs is enriched in S. carteri because of their application as part of the probiotic consortium. Microbiomes of both sponges are restructured, although BMCs are not incorporated in any C. crassa sample. Both species are visually healthy and efficiently pumping water at the end of the experiment. These results indicate that BMC inoculation in nearby corals is unlikely to affect sponge health or performance negatively, even when sponge-native BMCs are enriched in their microbiome, suggesting an opportunity for the development of probiotics for sponges.