design: DNA was extracted using the Qiagen QIAmp DNA Microbiome kit (Qiagen, Hilden, Germany) using a modified protocol for coral tissue (Voolstra et al. 2023; https://doi.org/10.5281/zenodo.6523532). Extracted DNA was sent to the NGS Competence Center Tbingen, Germany, for library preparation and sequencing of the internal transcribed spacer 2 region (ITS2). Amplicon libraries were prepared using the primers SYM_VAR_5.8S2 and SYM_VAR_REV (Hume et al. 2018 https://doi.org/10.7717/peerj.4816) and samples were sequenced on an Illumina MiSeq platform (MiSeq v3; 600 cycles, PE300). Site names: SA: Al Saada Reef; SY: Saadiyat Reef; SI: Snoopy Island (also referred to as AA: Al Aqah).