Blog Post Twenty-Seven
#COLORSOFTHEOCEAN_27
This photo depicts a stressed Cauliflower Coral. It’s scientific name is Pocillopora meandrina. It’s Hawaiian name is Ko’a. It is one of a few important reef building corals here in Hawaii. This coral is a surge tolerant species found in the surge/slope zone of the reef system. The color can range from that golden brown shade on the right side, to a more pink hue.
This particular image is striking because half of the coral head is alive, while the other half is not. Between 2014-2017, our Cauliflower corals have been experiencing what is known as coral bleaching. This occurs due to a variety of stressors. Some of which may include higher or lower ocean temperatures, too much sunlight, extreme low tides, pollution, and or chemicals from runoff. Coral has a symbiotic relationship with zooxanthellae. Zooxanthellae are algae that live in the tissue of coral and provide not only the color to the coral but are it’s primary food source, as they are able to photosynthesize and provide food to the polyps.
When zooxanthellae are stressed, they will expel themselves from the tissue of the coral polyps. Therefore, leaving the coral white and colorless. That is where the term bleaching comes in. However, the coral is not dead just because it is bleached. The polyps can survive for a bit, but do need the zooxanthellae to return in order to survive long term. While alive, the corals tissue secretes a mucus to prevent tiny seaweed or turf algae from moving in so to speak. Once the polyps die, they no longer can secrete this mucus and the algae will take over and colonize the surface. This is what you are seeing in this photo on the left side. Now the problem is that the turf algae will try to crepe over and overtake the healthy coral. As long as the healthy coral stays healthy, it will push back the algae with that secreted mucus. Coral and algae are always competing on the reef. Both are necessary, in moderation, for a healthy reef system.