A total of two replicate fragments (ramets) from 16 genotypically distinct host colonies (genets) were collected from the Mote Marine Laboratory in situ coral nursery in August 2015. In September 2015, another set of two ramets from 15 of the same genets of Acropora cervicornis were collected from the Mote Marine Laboratory in situ coral nursery (one genotype, G20, was not available due to high mortality rates). By this time the nursery corals had been experiencing anomalously high water temperatures reaching approximately ~2° Celsius (C) above historical averages, represented by 8 degree heating weeks (DHWs) under NOAA's Coral Reef Watch products (http://www.coralreefwatch.noaa.gov). These ramets were the same individuals utilized in Muller et al. (2018) to assess changes in disease susceptibility prior to and after bleaching. Genotypes were delineated in that study via microsatellite genotyping (Baums et al., 2005). When corals appeared healthy (i.e., no visual signs of bleaching) genotype 3 was completely resistant to white band disease, and genotype 7 had only 1 out of 5 replicates succumb to disease after exposure. Genotypes 3 and 7 both were resistant to white band disease even after bleaching. All ramets hosted Symbiodinium fitti, the main species of Symbiodiniaceae found in the Mote A. cervicornis nursery corals (Muller et al. 2018, Parkinson et al., 2018). All corals sampled in September were visibly bleached and showed a significant reduction in photochemical efficiency using Pulse Amplitude Modulator fluorometry (see Muller et al., 2018). Upon returning to the lab, all samples were flash-frozen in liquid nitrogen and stored in at -80°C until processing. A total of two polyps were scraped from each replicate using a sterile razor blade, and total DNA was extracted from polyp tissue using the MoBio Powersoil kit.

The bacterial community dynamics of each sample was analyzed using 16S rRNA Illumina sequencing on the MiSeq platform. Amplification of the 16S rRNA gene was conducted using the 515F-806R primer set, which targets the V4 region of the 16S rRNA, with barcodes on the forward primer (Apprill et al., 2015). A polymerase chain reaction (PCR) was performed using the HotStarTaq Plus Master Mix Kit (Qiagen, USA) under the following conditions: 94°C for 3 minutes, followed by 28 cycles of 94°C for 30 seconds, 53°C for 40 seconds and 72°C for 1 minute, followed by a final elongation step at 72°C for 5 minutes. PCR products were checked on a 2% agarose gel to determine the success of amplification and the relative intensity of bands. Multiple samples were pooled together in equal proportions based on their molecular weight and DNA concentrations. Pooled samples were purified using calibrated Angencourt Ampure XP beads (Beckman Coutler, CA, USA). Then the pooled DNA library was generated using the Illumina TruSeq DNA library preparation protocol. A PCR negative control was included in library preparation but did not produce a viable library. Paired-end sequencing was performed at MR DNA (http://www.mrdnalab.com, Shallowater, TX, USA) using a single flow cell on a MiSeq following the manufacturer’s guidelines.

Known problems/issues:
Genotype 20 was not sampled after bleaching due to mortality.