Colony preparation and acclimation
After collection, the coral colonies were placed in an outdoor tank with
opaque roof supplied with unfiltered flowing seawater to acclimate for a
week. Each colony was fragmented in four pieces using a tile saw, tagged
and all non-coral tissue area was cleaned and covered in reef-safe
epoxy. The colony fragments, here referred as “coral nubbins”, were
left acclimating in the indoor system for two weeks (ambient temperature
25°C ± 1°C). Using coral nubbins in laboratorial experiments is a way to
expose the same colony and microbiome to different treatments, allowing
for assessment of genetic variability among treatments, as well as
reducing the number of coral colonies collected. The nubbins were
monitored and only healthy ones, assessed by recovery of the coring
process (outward growth as opposed to tissue regression) and visual
endosymbiont function as measured by color and fluorescence readings
(Fv/Fm > 0.6) with a pulse amplitude modulated fluorometer
(DIVING-PAM Walz Inc.) were used in the experiments.