Algal symbiont density of coral Xenia umbellata in a aquarium experiment

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. After vortexing 10 µL was loaded onto a haemocytometer. Cells in the outer grids of both chambers were counted under a light microscope (two counts per sample). Data were normalised to the initial slurry volume and colony surface area. Xenia umbellata originates from the Red Sea.