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MESA: Deep-sea Coral Communities

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Coral communities in Alaskan waters are highly diverse and include six major taxonomic groups: true or stony corals (Order Scleractinia), black corals (Order Antipatharia), true soft corals (Order Alcyonacea) including the stoloniferans (Suborder Stolonifera), sea fans (Order Gorgonacea), sea pens (Order Pennatulacea), and hydrocorals (Order Anthoathecatae). One hundred and forty one unique coral taxa have been documented from Alaska waters and include 11 species of stony corals, 14 species of black corals, 15 species of true soft corals (including six species of stoloniferans), 63 species of gorgonians, 10 species of sea pens, and 28 species of hydrocorals. All corals found in Alaska are azooxanthellate and satisfy all their nutritional requirements by the direct intake of food. They are ahermatypic, or non-reef building corals, but many are structure forming. The degree to which they provide structure depends on their maximum size, growth form, intraspecific fine-scale distribution, and interaction with other structure-forming invertebrates.

Deep-sea corals are widespread in Alaska and have been reported as far north as the Beaufort Sea. Corals occur from the shallow subtidal zone to the deep ocean trenches (Table 1). For example, seapens have been found as shallow as 3 m depth and black corals and sea fans have been found at a depth of 4784 m on Gulf of Alaska seamounts. In addition to general factors controlling coral distribution such as current regimes and the presence of hard substrates, temperature tolerance appears to play a role in the geographic and depth distribution of some deep corals.

Many species of micro-fauna, particularly brittle stars and amphipods, are found living on deep-sea corals
Many species of micro-fauna, particularly brittle stars and amphipods, are found living on deep-sea corals.

In Alaska, many commercially valuable fish and crab species and other non-commercial species are associated with deep corals. Most associations are believed to be facultative rather than obligatory. Fish and crabs, particularly juveniles, use coral habitat as refuge and as focal sites of high prey abundance. Some shelter-seeking fishes such as rockfish may use coral habitat as spawning and breeding sites.

Table 1
Taxa # Species Depth range (m)
Scleractinia 11 24-4620
Antipatharia 14 401-4784
Alcyonacea 9 10-3209
Stolonifera 6 11-591
Gorgonacea 63 6-4784
Pennatulacea 10 3-2947
Anthothecatae 28 11-2130
Total 141 3-4784

Bob Stone
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries

Auke Bay Marine Station
11305 Glacier Hwy
Juneau AK 99801

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