Hawai'i Coral Reef Network

Overview of Ecology of Coral Reefs in Hawai,'i

Brian N. Tissot
Kalakaua Marine Education Center
University of Hawai’i at Hilo Hilo

A. Uniqueness of Hawaiian Ecology

 The ecology of coral reefs in Hawai'i is unique compared to reefs in other tropical areas. Hawaiian reefs are unique for several reasons:

1. They are geologically young and therefore not as well developed as other reefs. Most reefs in the windward islands of Hawai'i, Maui, O'ahu and Kaua'i are small and occur relatively close to shore. As these reefs grow and develop they are called fringing reefs, which eventually develop into barrier reefs, which occur in Kaneohe Bay on O'ahu and on the south shore of Moloka'i. There is a general westward trend towards greater reef development which coincides with the geologic ages of the islands. Superimposed upon this pattern, however, is the effects of wave exposure: in general more sheltered leeward coasts have reefs with greater coral cover than wave-pounded windward coasts (see Grigg, 1983).

Narrow coral reef at Puako on the Big Island, typical of young Hawaiian coral reefs

2. As a consequence of their younger age and the general absence of barrier reefs in the windward islands, Hawaiian reefs are generally less productive than other reefs. With smaller reef areas and the absence of lagoons that trap and retain both coastal and terrestrial runoff, Hawaiian reefs are generally more nutrient poor and therefore lack a high abundance of filter feeding animals such as soft corals, sponges, tunicates, and bivalves. As a result, Hawaiian reefs are more clearly dominated by corals.

3. Due to the geographic isolation of the Hawaiian Islands they are less diverse that other reefs, especially those in the nearby Indo-Pacific province to which they belong. For example, in Hawai'i there are about 40 species of reef building corals; in the western Pacific island of Palua there are over 300! One consequence of lower diversity is that reef-building corals in Hawai'i are less specialized and thus more generalized in their distribution than species elsewhere. Furthermore, a relatively few number of corals dominant Hawaiian reefs. There is a unique advantage to science here, however, because Hawaiian reefs are far easier to study!

B. Coral Reef Zonation in Hawai'i

 In response to variation in environmental conditions near the shoreline, coral reefs exhibit zonation where the abundance and composition of the coral community varies according to distance and depth from shore. Wave exposure is the primary factor causing zonation in Hawai'i but gradients in sedimentation, salinity, and temperature are also important (see Dollar, 1982). The following is a summary of zonation patterns typical of Hawai'i. Common names are linked to descriptions in the Marine Life of Hawai'i section.

Reef Zonation Patterns

Reef flat zone
(0-2 m)

Reef bench zone
(2-10 m)

Corals are generally sparse here and dominated by cauliflower coral intermixed with boulders. Lobe coral is abundant along with some cauliflower coral, other uncommon corals (e.g., Leptastrea & Pavona) and sand.
This area has numerous boring urchins in holes. Boring urchins, sea cucumbers, numerous snails and Christmas tree worms are common.
Surgeonfishes dart in and out of the reef flat feeding on turf algae. Surgeonfishes, wrasses, damselfish, triggerfish and puffers are common.


Reef slope zone
(10-30 m)

Rubble zone
(30-40 m)

Finger coral is the most common species along with lobe coral. This area usually consists of lobe and finger coral rubble sloping into sand.
Wana, slate-pencil urchins, sea cucumbers and christmas tree worms are common. Sea cucumbers occur here.
Surgeonfishes, wrasses, butterflyfish, goatfish, and snappers are common. You may see damselfish, triggerfish and garden eels here.


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Last update: 1/25/2005