Know Your Coral

Photo Credit: Matthew Wheeler, Trilogy Excursions

Coral reefs are underwater ecosystems, hosting over thousands of marine organisms. They come in blues, reds, yellows, browns, greens, and purples, making the ocean floor a rainbow. Despite looking like rocks, corals are a living invertebrate. They typically live in colonies and are made up of individual identical polyps. Each polyp has a mouth and stomach. They excrete an exoskeleton at the base giving the coral species its shape. The polyps continue to multiply resulting in the growth of the coral. All corals have a symbiotic relationship with microscopic algae called zooxanthellae. The zooxanthellae photosynthesize and provide the coral with energy-rich compounds while the coral provides a hard structure for the zooxanthellae to live in. The zooxanthellae also give the coral its characteristic color.

Illustration Credit: Sea Horse Run! Tammy Carter Bronson

For an animal that doesn't seem to move or to be actually alive, how to corals eat?

Corals get food by catching small fish and plankton in their tentacles, and from their photosynthetic algae.

People travel thousands of miles to swim in a warm ocean and glimpse the colorful corals, but why is coral important?

Corals provide a food source and shelter for small reef fish. They also work as barriers around islands, softening the blow of incoming waves. Corals also are a source of nitrogen and other nutrients supporting the food chain.

Corals are very slow growing, about 0.4in a year. This slow growth means corals have a hard time recovering from a threat or disease. One of the main reasons corals get sick is from warmer ocean temperatures. A water temperature change of only 1-2Deg C can kill some species of corals. Another threat can come from sedimentation, runoff, or pollution. This puts excess nutrients into the water column which then settle onto the coral. These high nutrient events can be caused naturally or by human impact. When coral gets stressed out, due to any one of these threats, the zooxanthella could leave the coral and go up into the water column. This leaves the coral skeleton looking white, known as coral bleaching. The coral can live without the zooxanthella for a short time, but eventually, the coral will start to starve. If the zooxanthellae do not return to the coral, the coral will die.

Some common coral you will see in Maui:

Pocillopora meandrina - cauliflower coral

A solid coral with a dome shape and small flattened branching fingers. Color varies from brown to pink. P. meandrina is found in a range of habitats; protected lagoons, exposed reefs, and lower reef slopes. This coral reproduces asexually by fragmentation. P. meandrina is one of the coral species more easily suitable to threats.

“Fragmentation - Each of these fragments develop into mature, fully grown individuals that are clones of the original organism”.

Photo Credit: Matthew Wheeler, Trilogy Excursions

Porites lobata - smooth mounding coral

This type of coral varies in size and shape due to where it is found. In calm waters, it will take the shape most commonly seen in Maui, that of smooth, rounded, pinnacles. It can range in color from yellow, brown, to green. P. lobata is found in the Pacific and the Indian Ocean. This coral species is a more resilient species to threats.

Photo Credit: Matthew Wheeler, Trilogy Excursions

Montipora flabellata - blue rice coral

An encrusting coral which is different from the previous two mentioned. M. flabellata grows mostly flat across the reef. It is a bright blue coral, making it one of the more picturesque. This coral is known as a scleractinian, or stony coral. M. flabellata is a special to Hawaii because it is only found in Hawaii, termed “endemic”. It can be found in shallower waters down to 10meters depth.

Photo Credit: Linda Preskitt, Eyes of the Reef Hawaii

Due to their vulnerability and slow growth it is imperative that we keep our coral reefs healthy.

Here are 10 ways suggested by the Nature Conservancy to help reduce our impact on coral:

  1. Conserve water: The less water you use, the less runoff and wastewater will pollute our oceans.

  2. Help reduce pollution: Walk, bike or ride the bus. Fossil fuel emissions from cars lead to ocean warming which causes mass-bleaching of corals and can lead to widespread destruction of reefs.

  3. Research what you put on your lawn: Although you may live thousands of miles from a coral reef ecosystem, these products flow into the water system, pollute the ocean, and can harm coral reefs and marine life.

  4. Dispose of your trash properly: Don't leave unwanted fishing lines or nets in the water or on the beach. Any kind of litter pollutes the water and can harm the reef and the fish.

  5. Support reef-friendly businesses: Ask the fishing, boating, hotel, aquarium, dive or snorkeling operators how they protect the reef. Be sure they care for the living reef ecosystem and ask if the organization responsible is part of a coral reef ecosystem management effort.

  6. Plant a tree: Trees reduce runoff into the oceans. You will also contribute to reversing the warming of our planet and the rising temperatures of our oceans.

  7. Practice safe and responsible diving and snorkeling: Do not touch the reef or anchor your boat on the reef. Contact with the coral will damage the delicate coral animals, and anchoring on the reef can kill it, so look for sandy bottom or use moorings if available.

  8. Volunteer for a coral reef cleanup: You don't live near a coral reef? Then do what many people do with their vacation: visit a coral reef. Spend an afternoon enjoying the beauty of one of the most diverse ecosystems on the Earth.

  9. Contact your government representatives: Demand they take action to protect coral reefs, stop sewage pollution of our oceans, expand marine protected areas and take steps to reverse global warming.

  10. Spread the word: Remember your own excitement at learning how important the planet's coral reefs are to us and the intricate global ecosystem. Share this excitement and encourage others to get involved.

By Conservation and Education Director, Magen Schifilitti