Differential Symbiodiniaceae Association With Coral and Coral-Eroding Sponge in a Bleaching Impacted Marginal Coral Reef Environment

Marginal reefs are known for severe stress-inducible perturbations such as high sedimentation, eutrophication, ocean warming, and acidification from anthropogenic climate change. The corals striving in stressful environments develop physiological adaptations induced by differential genomic expressions or association with thermal stress-tolerant algal symbionts (Symbiodiniaceae). Despite adaptations, threatened other space competitors algae sponges. Coral-eroding sponges belonging to the Cliona viridis complex one that also associate Symbiodiniaceae photosymbiont. diversity of associates coral sponge same ecosystems is scarcely known. In present study, community structure Turbinaria mesenterina , a newly described coral-eroding thomasi their surrounding seawater was determined nearshore marginal reef along central west coast India. results revealed significantly higher relative abundance Durusdinium Gerakladium than Symbiodinium Cladocopium seawater. Interestingly, both investigated host species showed sponge. beta analysis Permutational multivariate variance (PERMANOVA) confirmed significant differences profiles between coral. thermotolerant genera different hosts suboptimal conditions. Our field surveys suggested bleaching resistance T. despite fact sea surface temperature reached threshold 31°C during periods years 2015, 2016, 2017, 2018, 2019. Therefore, tolerance may be attributed respective photosymbiont associations. Furthermore, indicated host-specific selection local environment. Although these observations provide valuable biological insight, more research needed understand tripartite sponge-coral-symbiont together evaluate competitive fitness holobionts.