Hawaiian Coral Reefs

The extensive coral reef system of the Hawaiian Island chain (which extends from Midway Island to the big island of Hawaii) comprises more than 5000 square miles of total area. Although built by only two families of hermatypic coral, this impressive

system of coral reefs is unrivaled by any other set of reefs in U.S. waters, including those in the Caribbean. (In general, Pacific reef systems show a greater biodiversity than their Atlantic counterparts. Pacific reef habitats are home to many more coral species, both stony and soft, four times more mollusk species, and more than three times the species of reef fish.) Deriving mostly from western Pacific reef habitats, the creatures that inhabit Hawaiian waters have evolved along slightly different lines than their ancestors. As a result, nearly a third of the Hawaiian fish species are found in no other place on the Earth. Indeed, a fifth of the algae species, mollusks, and sea stars found in Hawaiian waters are totally endemic to the islands.

In some cases, species that are quite common in other parts of the Pacific Ocean, are rare or absent in Hawaiian waters. This phenomenon is dramatically displayed in the reef-building corals themselves. In nearly every other reef system the world over, the Acroporid corals are the principal reef-builders. In Hawaii, they are somewhat rare, their place being taken by the Poritid and Pocilloporid corals.

In general, the Hawaiian reef habitat supports fewer species than the extensive reef systems in the south Pacific. For example, more than 2000 species of fish have been identified in the waters surrounding the Philippine Islands while only 450 are found in Hawaiian waters.

The characteristics that seem to set Hawaiian reef habitats apart from those in other parts of the Pacific basin are the result of isolation and different water temperatures. Hawaiian waters range in temperature from 76º F to 81º F, a bit cool for optimal coral growth, but still warm enough for some 50 species of shallow-water corals to thrive.

Although somewhat stressed by the cooler waters surrounding the Hawaiian Island chain, the reef-building corals still comprise a good part of the reef system. But they are not the main contributor! That role goes to the encrusting, CaCO₃-secreting red coralline algae that are so common in Hawaiian waters. In short, Hawaiian limestone reefs are mostly composed of calcareous algal deposits and coral reef rock.

Three distinctive reef environments exist in the Hawaiian Island chain, each dominated by a particular species of reef-building coral and each defined by depth and wave energy. The first reef environment occurs only in the most protected, low energy locations around the islands. These include shallow waters in protected bays or deeper waters on the calm, leeward side of the islands. It is in these relatively tranquil waters that Hawaii's second most common reef-building coral, the Finger Coral, is most abundant. The second reef environment occurs in locations dominated by moderate wave action and very shallow water. This situation occurs along most of the semi-protected coasts of the islands and it is here that Hawaii's most common reef-building coral, the Lobe Coral, thrives and dominates. The third reef environment occurs in the least protected, highest energy locations along the wave-battered, windward sides of the islands. This situation occurs in shallow waters that are fully exposed to turbulent wave action. It is in these waters that Hawaii's most important colonizing coral, the Cauliflower Coral, is most common.

The coral reefs of Maui provide an excellent example of the various reef environments that can be found in the Hawaiian Island chain. The island is fringed by an extensive system of coral reefs, many of which are readily accessible by experienced divers. Representing some of Hawaii's finest coral reef habitats, the coral gardens of Maui present a complex and colorful ecosystem.

A number of large and intricate reef structures with good relief and a rich and varied community of organisms can be found along the periphery of the island. Just off the northwest coast of Maui, some particularly impressive coral reefs can be found in the bays and in the waters surrounding the headlands. The reefs at Honokohau Bay, Kapalua Bay, Honanana Bay, Nakalele Point, Mokolea Point, and Kahakuloa are the most impressive.

The north-central coastline of Maui has several equally impressive reefs, the best of which is in Maliko Bay. The reefs at Pauwela Point, Kaelua, and Ke'anae Peninsula are nearly as magnificent.

Along the southern coast of the island, a number of rich and colorful coral reefs can also be found. Particularly impressive are the reefs at Olowalu, Nahuna Point, Ahihi Bay, La Perouse Bay, Haleki'i, and Nu'u Bay.