Coral restoration in a stressful environment: Disease, bleaching, and dysbiosis in Acropora aspera in Guam, Micronesia

Despite advances in coral restoration science, challenges imposed by rapid environmental change impede progress. Here, we report mortality from disease and bleaching in an introduced nursery-reared population of the staghorn coral <i>Acropora aspera,</i> in Guam, Micronesia. We present disease progression, incidence, synergies between stressors, and response of the coral microbiome. Microbiome composition in nursery vs. outplanted corals indicated dysbiosis induced by the transition to poorer water quality. However, among outplants, there were no differences between diseased tissues, visually healthy tissues on the same infected colony and tissues from non-infected colonies, suggesting that outplanting into a stressful environment may have compromised coral immune response, increasing susceptibility to disease and bleaching. Our study highlights that outplanting is inherently physically stressful, thus underscoring the need for understanding the microbiome's role in the coral transplantation stress response. We suggest workflows to minimize stress and improve restoration in the face of environmental challenges.