Most reef-building corals contain photosynthetic algae, called zooxanthellae, that live in their tissues. The corals and algae have a mutualistic relationship. The coral provides the algae with a protected environment and compounds they need for photosynthesis. In return, the algae produce oxygen and help the coral to remove wastes. Most importantly, zooxanthellae supply the coral with glucose, glycerol, and amino acids, which are the products of photosynthesis. The coral uses these products to make proteins, fats, and carbohydrates, and produce calcium carbonate. (Source: NOAA Ocean Service Education)
We got to see these coral polyps and their symbiotic algae photosynthesising, under UV light, in the educational Underwater World aquarium at Birdworld in Farnham. It’s mesmerisingly beautiful! The colour that we associate with coral reefs is derived from the algae living within the tissue. When a reef is put under physical stress, the coral polyps actually expel the algae leaving the structures a stark white. This is the tragic, mass death of large areas of reef that we call “bleaching”. Seeing the living coral made this disatrous phenomenon all the more real to me. I’m posting this image for Wex Mondays this week and I hope that it will lead others to think about the plight of our precious coral reefs.