One colony per tank was randomly selected every 7 days and stored at -20°C. On analysis day, colonies were thawed, homogenised in 10 ml demineralised water, and the slurry volume was measured. 2ml of the slurry was aliquoted, centrifuged twice to separate algal cells from coral tissue, and resuspended in demineralised water. In a darkened room, pellets were resuspended in 2 ml of 90% acetone, vortexed, and stored at 4°C for 24 h. After centrifugation, samples were split into two 1 ml cuvettes and measured on a UV-Spectrophotometer (663 nm & 630 nm) against a calibration curve. Each subsample was measured three times, with readings normalised to slurry volume and Symbiodiniaceae cell count. Xenia umbellata originates from the Red Sea.

Study location: Aquarium experiment at the University of Bremen, GermanyTreatments: 3 carbon enrichment treatments of 20 mg C/L. DOM (glucose), 2. POM (phytoplankton), 3. POM (zooplankton)Date of study: May 2022Duration of study: 28 daysSpecies information: Xenia umbellata native to the Indo-Pacific and Red Sea