Coral bleaching occurs when coral polyps expel algae (Zooxanthellae) that live inside their tissues. … Bleached corals continue to live but begin to starve after bleaching. Some corals recover. When algae begin to attach to corals, the chances of reviving are low. Above-average sea water temperatures caused by global warming is the leading cause of coral bleaching.

I always observe corals in the Marshall Islands. This bleaching phenomenon can be seen in a much wider ocean side than in 2014 and 2016. Most of them are [Acropora austera], [Acropora intermedia (nobilis)], [Acropora cytherea] and [Acropora listeri (danai)] at Ocean side. also, [Porites lutea] and [Porites rus] at Lagoon side. This time bleaching phenomenon is particularly stand out around the outside of the atoll.

Around the beginning of October 2019 they started showing signs and then turned completely white (Coral bleaching). In November, algae began to attach to various corals. When algae attaches to corals, the Zooxanthellae do not return there and no new eggs attach (implantation). That means, in order for them to revive, the Zooxanthellae must return before the algae attach.

I have never seen such wide area coral bleaching in this place for more than 10 years.
Coral reefs are in serious danger all over the world.

About: Zooxanthellae (Wikipedia)


  • Sea water temperature rise by climate change
  • Water quality (pollution of seawater, garbage dumping and polluted soil)
  • Insufficient photosynthesis by cloth and garbage covering coral
  • Decreased photosynthesis by abnormal plankton outbreak
  • Crown-of-thorns starfish
  • Excess ultraviolet rays
  • White syndrome (Infection)
  • Various stress   etc…

When the destruction rate is higher than the coral development rate, the island cannot recover. It is highly important to live while thinking about coral conservation.

Our modern way of life brings us wealth but also produces tons of waste. When you throw waste into the sea, it damages our valuable corals.


  • Cradle of Life:  Many fish, shellfish, prawns, crabs and seaweed live and grow in coral reefs, Coral reefs are also a place to spawn for various kinds of fish.
  • Underwater CO2 purification function:  Corals consume CO2 and calcium from seawater by polyps. Calcium forms a skeleton, and CO2 is converted to O2 by photosynthesis.
  • Food, fishery and resources:  Coral nurtures the fish and seafood that we eat.
  • Protecting islands:  Coral reefs act as a breakwater. They weaken sea waves and protect the seashore and islanders.
  • Tourism, education, research and landscape:  Beautiful landscapes are a valuable tourism resource. They can become marine recreation areas for activities such as Snorkeling and Scuba diving.

Most of the Marshall Islands are made of coral and other life in the reefs. We must not forget the importance of coral.

Photo © Hiro/Hiroaki Ueda @ RAYCREW / 16th/Nov/2019


I will continue to observe the corals in the Marshall Islands.