Corals: The Foundation of the Reef

coral reef

Interesting fishes and marine mammals seem to garner our affection when diving and doing underwater photography in Hawaii. But there is an animal that is the foundation of the reef that deserves a look- corals!

Coral reefs have the distinction of being planet earth’s largest living structures. Even though they may look like a rock or a plant, coral, or ‘āpapapa in Hawaiian, are actually animals.

How coral reefs are formed

coral reef Maui

We’re going to talk about coral sex for a moment, but don’t close your eyes—it’s very “G” rated 😊. Here is a bit about coral formation:

1. Coral reefs release eggs and spermatozoa (gametes).

2. After fertilization (meeting of a male and female gamete), a ciliated larva called planula is formed.

3. The larva will attach itself to a place favorable to its development and form a flat disc.

4. A polyp will form and then bud (each polyp secretes a hard exoskeleton, made up of calcium carbonate, as well as an internal limestone skeleton that remains in place even after the death of the animal), to complete the formation of coral.

Continuous budding of the polyps makes it possible to enlarge the coral colony which, over time, forms the reefs.

It’s important to note that polyps could not live and reproduce without their symbiotic relationship with zooxanthellae algae as a food source. While the algae provides the animal with the necessary nutrients, the polyp in return releases carbon dioxide which allows the algae to develop and also to carry out photosynthesis which will gives color to corals.

Types of coral found in Hawaii

Laying at the northern most point of coral distribution in the Indo-Pacific, Subtropical Hawaii has less than 80 species of coral. This is compared to over 500 species found further south around Indonesia and the Philippines, also known as the Coral Triangle.

The three most common types of coral we have in Hawaii are Porites (smooth coral), Montipora (rice coral) and Pocillopora (small branching coral).

Smooth mounding coral (Porites lobata) with algae by Pvandyke3. CC license.

Rice coral (Montipora capitata) by GRIDArendal, CC license.

Cauliflower coral (Pocillopora meandrina) by USFWS Pacific, CC license

How to differentiate coral species

Corals are also identified by their shape, color and size. The common name of corals are a clue as to which one you are seeing. While diving, color is often the first clue, with a closer examination of shapes to tell for sure.

Coral predators

Along with other threats to coral, such as human impact and coral disease, other marine life eat coral. The most risky to coral reefs are Crown of Thorns (COTS). In the starfish family, COTS canproduce up to 60 million eggs during a single spawning season, and start eating coral at 6 months of age.

COTS can move quick from one area to another, making management difficult. However, early detection is important. If you see a large number of COTS while diving, please report the location online.

Coral are a protected species

Hawai‘i’s coral reefs are a fragile ecosystem that often are damaged by people standing on coral heads or removing living coral. We know divers are more environmentally aware through their certification training. Divers can help be ambassadors, as those using the ocean should not remove or otherwise damage coral. Avoid grabbing onto or letting fins, tanks or other gear hit coral. Coral (as well as with rocks to which marine life is attached) is protected under Hawai‘i state law. Breaking, taking, damaging, or selling coral obtained through illegal means is not permitted, and carries hefty fines.

When going out on charter with Lahaina Divers, we first listen to a Hawaiian chant, asking for permission to enter the ocean. We also share kuleana (loosely translated means responsibility) to care for corals and other marine life along our journey.