The Hawaiian reef coral, Montipora dilatata, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of coral

Coral

Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

 in the family Acroporidae

Acroporidae

Acroporidae is a family of small polyped stony corals in the phylum Cnidaria. The name is derived from the Greek "akron" meaning "summit" and refers to the presence of a corallite at the tip of each branch of coral. They are commonly known as staghorn corals and are grown in aquaria by reef...

.

Description

Morphology of this species can be quite variable. Colonies may be any combination of encrustations, plates, knobs, and branches. Montipora dilatata is a glabro-favoleate type that is characterized by a very smooth surface. Colonies are usually purple or brown and reach 3 feet (1 m) in diameter. The species only occurs in the Hawaiian archipelago, in Kaneohe Bay, Oahu

Oahu

Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...

, and in the Northwestern Hawaiian Islands

Northwestern Hawaiian Islands

The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niihau. They are administered by the U.S. state of Hawaii except Midway Atoll, which has temporary residential facilities and is...

 (NWHI) at Midway Atoll

Midway Atoll

Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...

, Pearl and Hermes Atoll

Pearl and Hermes Atoll

The Pearl and Hermes Atoll , is part of the Northwestern Hawaiian Islands. Named after two English whaleships, the Pearl and the Hermes, that wrecked there in 1822, a few, small, sandy islands exist, contained within a lagoon and surrounded by a coral reef. These islands are devoid of vegetation,...

, Lisianski Island

Lisianski Island

Lisianski Island is one of the Northwestern Hawaiian Islands, with a land area of and a maximum elevation of above sea level. Honolulu is away, to the southeast. Linked to Lisianski are the extensive Neva Shoals...

, Laysan Island, Maro Reef

Maro Reef

Maro Reef is a largely submerged coral atoll located in the Northwestern Hawaiian Islands. It was discovered in 1820 by Captain Joseph Allen of the ship Maro, after whose ship the reef was named. With a total area of , it is the largest coral reef in the Northwestern Hawaiian Islands...

, and French Frigate Shoals

French Frigate Shoals

The French Frigate Shoals is the largest atoll in the Northwestern Hawaiian Islands. Its name commemorates French explorer Jean-François de La Pérouse, who nearly lost two frigates when attempting to navigate the shoals...

.

Ecology

This species requires calm water in sub-tidal environments. The species is easily broken into fragments by storms or bioerosion

Bioerosion

Bioerosion describes the erosion of hard ocean substrates – and less often terrestrial substrates – by living organisms. Marine bioerosion can be caused by mollusks, polychaete worms, phoronids, sponges, crustaceans, echinoids, and fish; it can occur on coastlines, on coral reefs, and...

, with the fragments readily growing into new colonies. This species occurs in lagoons and bays and appears to be restricted to shallow, low-water motion environments. This species is presently very rare in Kaneohe Bay, but at one time was more abundant and occurred in large patches on some of the reef flats.

Threats and Conservation

It has declined significantly over time and only 3 colonies were found in a 2000 survey. The main threats to M. dilatata include: 1) vulnerability to coral bleaching due to high temperatures (it was the first species to bleach during the 1996 event in Kaneohe Bay); 2) fresh water kills and exposure at extreme low tide; 3) habitat degradation and modification as a result of sedimentation, pollution, alien alga species (Gracilaria salicornia, Kappaphycus and Eucheuma

Eucheuma

Eucheuma is a general term used to describe a group of red seaweeds/seaplants representing the Tribe Eucheumatoideae, used in the production of Carrageenan, an important product used in cosmetics, food processing and industrial uses, as well as a food source for those living in Indonesia and the...

spp. algae) and invasive green alga (Dictyosphaeria cavernosa) in Kaneohe Bay; 4) a limited distribution; and 5) damage by anchors, fish pots, swimmers and divers.

Two other species, M. turgescens at Kure Atoll and M. cf. dilatata (recorded at one site out of 30 sites surveyed at Maro Reef in 2000-2002) are similar, and genetic analysis should be done to confirm their separation into distinct species.

The Hawaiian reef coral is a U.S. National Marine Fisheries Service Species of Concern. Species of Concern are those species about which the U.S. Government’s National Oceanic and Atmospheric Administration, National Marine Fisheries Service has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S. Endangered Species Act (ESA).

Coral collection is not allowed in the State waters of Hawaii without a research permit.