FACT OF THE WEEK: Bio-Fluorescent Coral Flaunts Underwater Light Show

MORE ON THIS: It is easy to see the beauty of coral reefs when snorkeling or diving during the day, but have you ever seen the colors of coral at night?

Coral reefs are known to put on a light show known as bio-fluorescence.  A family of proteins provides this fluorescence by absorbing one color and emitting another.  Each protein provides a different color; the most common is the green fluorescent protein known as GFP.  When the wavelengths of color are absorbed then re-emitted, some of the energy is lost.  This changes the wavelength, which determines the color.

Species of coral known to give off this fluorescence are found in Hawai‘i and can be seen on night dives with special dive lights.  If you’re interested in seeing this phenomenon, you can contact your local dive shop to ask about night diving to see fluorescent coral or, if you’d like to stay dry, you can visit the Maui Ocean Center which has some of this coral on exhibit.

It is unknown why fluorescence occurs, but there are speculations from scientists.  Some believe that it acts as a sunscreen for the coral.  Researchers also have proposed that the fluorescence creates light to allow algae to grow in deeper water; algae is the major food source of most corals.

Research is focusing on coral fluorescence for several reasons.  The first reason is due to the fragile state of coral reefs in our climate-changing world.  Some studies suggest that the intensity of the fluorescence can be a sign that the coral is under stress and may indicate that the coral is about to bleach.

Medical research is also greatly benefiting from coral fluorescence research.  The same proteins the corals use to fluoresce are being used to help monitor biological processes within diseases to further understand how they work. This is done by using the fluorescence as a marker so scientists can watch cells divide or viruses spread.


  1. Roach, John. 2005. “Glowing Coral Proteins Aid Medical Research.” National Geographic. http://news.nationalgeographic.com/news/2005/01/0112_050112_coralproteins.html
  2. Roth,  Melissa S., Fran, Tung-Yung, Deheyen, Dimitri D. 2013. “Life History Changes in Coral Fluorescence and the Effects of Light Intensity on Larval Physiology and Settelement in Seriatopora hystrix.” Plos One. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0059476
  3. University of California – San Diego. 2013. “Fluorescent light revealed as gauge of coral health: Mysterious glow of light found to correlate with coral stress prior to bleaching.” Science Daily. www.sciencedaily.com/releases/2013/03/130312092918.htm.

Written by Sarah Mousel

Help Protect Maui’s Coral Reefs and Manta Rays

Maui truly is blessed in being surrounded by an underwater wonderland. In addition to hosting one of the largest concentrations of humpback whales during their birthing season in the world, we are also lucky to have the chance to see other graceful, unique denizens of the deep, such as monk seals, several species of sharks and even manta rays.

Maui is one of a few places in the entire world with a resident population of manta rays. Olowalu Reef, off of West Maui, is home to an estimated 350 resident reef manta rays. In nearshore reef locations, manta rays congregate around “cleaning stations”, where Hawaiian cleaner wrasse eat parasites of  the skin of a manta ray. Manta rays are also thought to breed in the shallow coral reef habitat.

Unfortunately, both species of manta ray (Manta birostris and Manta alfredi) are currently listed as vulnerable by the International Union for the Conservation of Nature. Manta rays are hunted in some countries for their skin, their fins (for the shark fin soup trade) and for their gill rakers, which are used in some Chinese medicines. Since manta rays mature slowly and have few pups, they are especially susceptible to fishing pressures. Manta rays around Maui have also been spotted entangled in fishing line and some have even lost part of their fins due to this marine debris. Learn more from HAMER.

To raise awareness, Pacific Whale Foundation has just launched a seasonal conservation campaign to take action and help protect the coral reefs of Maui that resident manta rays depend on.

On Maui, proposed shoreline development near the Olowalu area would cause increased runoff, which would smother coral polyps. Encourage sustainable development and responsible environmental policies by supporting conservation minded local officials, no matter where you live. Be sure to clean up and recycle monofilament fishing lines with Pacific Whale Foundation’s fishing line recycling program. Much is still to be learned about manta ray populations, migrations, habitat use, and behavior. Help add to knowledge of these animals by donating any “belly shots”, with sighting location and date, to Hawaii Association for Marine Education and Research for mantas in Maui, or to Manta Trust, for mantas spotted in other parts of the world.  Good luck spotting these amazing ambassadors of the reefs!

Coral Reef Survey

Pacific Whale Foundation (PWF) was recently contacted by WHALE Environmental Services LLC and asked if we were interested in a collaboration, as this Oahu-based company was planning to undertake a pilot project to survey the West Maui coral reefs. PWF was very keen to take part, and so we made arrangements to take our research vessel, Ocean Protector, out as a diving vessel for a change.

Using a standardized method, we made very short dives at 14 coral reefs along the coast of West Maui, between Ma’alaea Harbor and Honolua Bay. While scuba diving, we took note of various factors which would be used to indicate reef health, such as:

  • the number of coral species observed
  • the number of fish species observed
  • signs of pollution
  • signs of erosion
  • signs of coral disease or bleaching
  • signs of fishing pressure
  • signs of stormwater entry at the site

It was interesting to see the stark differences between a healthy reef and an unhealthy reef. This project is a baseline study – meaning that we are recording the current state of these reefs so we have a measurable starting point and can monitor the reef and detect any changes in the future. In science it is very important to record a baseline so you know when changes are happening. You then have data on how fast or slow changes are occurring, or in what locations.

While we await the results of the report that is being prepared, the research department is back to its usual summer routine of carrying out transect surveys for dolphins and marine debris.