Wai‘anae Ecological Characterization

Marine Ecosystems

Wai‘anae's coastal and marine ecosystems are characterized by rocky intertidal zones, coral reefs, and offshore pelagic and deep sea marine environments. Intertidal zones provide rocky habitat to marine invertebrates and plants that are specifically adapted to constantly changing levels of exposure to waves and seawater. Coral reefs are found on the more protected leeward exposure of the Wai‘anae coast but are subject to infrequent but severe Kona storms. Offshore pelagic and deep sea ecosystems off the Wai‘anae coast are vast and support large marine animals like dolphins, whales, sea turtles, and the occasional endangered Hawaiian monk seal. Threats to coastal and marine ecosystems along the Wai‘anae coast include land-based and sea-based human activities, natural disturbances from storms, and large-scale global climate change phenomena such as sea level rise and increased sea surface temperature.

This section discusses Wai‘anae's marine ecosystems including intertidal communities, coral reefs, and offshore pelagic and deep sea communities. Special focus is also given to the marine mammals and sea turtles that commonly inhabit the waters off of the Wai‘anae moku. Additionally, this section discusses threats to these critical habitats and resources and management programs that have been developed to protect them.

Critical Marine Habitats and Resources

Coral Reefs. Coastal areas with high wave exposure generally have the lowest coral cover in O‘ahu, while bays and wave-protected coastal areas have the highest coral cover. Not surprisingly, coral cover is low along much of the Wai‘anae coast, due to the shallow, flat, and low-relief bottoms in this area. However, corals thrive on the artificial reefs off the Wai‘anae coastline, off of Mākaha Beach, and on the thermal outfall pipe at Kahe Point, just south of the Wai‘anae moku.

These areas are dominated by two coral species, Pocillopora meandrina and Porites lobata, and the reefs provide food and shelter for many fish and invertebrates. The reef at the Kahe power plant outfall is the subject of the longest running coral reef study in the world, with monitoring occurring continuously since 1971.

Hawaiian Monk Seal. The endemic and critically endangered Hawaiian monk seal (Monachus schauinslandi) is known in Hawaiian as "Ilio holo I ka uaua," which translates as "the dog that goes in rough water."

The Hawaiian monk seal, a federally listed endangered species, most commonly inhabits the Northwestern Hawaiian Islands. However, monk seals are occasionally sighted around the main Hawaiian Islands, including off Mākua Beach on the Wai‘anae coast. Prominent threats to monk seal populations include entanglement in fishing gear; disturbance by humans, which can cause seals to abandon haul-out areas and their pups; and predation by sharks.

Green Sea Turtle. The green sea turtle (Chelonia mydas), considered the most abundant sea turtle in Hawaiian waters, is listed as a threatened species under the federal Endangered Species Act. These turtles can be seen off the waters of Wai‘anae.

Threats to sea turtles occur from land-based and sea-based activities, such as loss of nesting habitat due to development, nest predation, boat collisions, entanglement in fishing gear, and ingestion of marine pollution. The U.S. Recovery Plan for Pacific populations of green turtles delineates reasonable actions that are considered necessary to recover and protect the species.

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