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Coral habitats on the Mid-Atlantic Ridge

Deep-sea coral habitats on seamounts on the Mid-Atlantic Ridge between Iceland and the Azores has now been described based on video surveys using ROV and bycatch from longline and trawl on the 2004 MAR-ECO expedition.

The picture shows a red soft coral of the genus Anthomastus, a bushy black coral (Antipatharia), and a stone coral (Lophelia pertusa or Solenosmilia variabilis).
Pål B. Mortensen  (Institute of Marine Research, Bergen, Norway) presented the results at the third International Deep-Sea Coral Symposium, which was held in Miami, November 2005.

- Corals were observed on most sites inspected from depths around 800 m down to around 2600 m. Octocorals dominated the coral fauna which comprised a total number of 30 taxa. The coral diversity was higher in the southern area compared with the northern, tells Mortensen.

Living scleractinians (Lophelia pertusa and Solenosmilia variabilis) were repeatedly observed on the seamounts but always with relatively small colonies. The deepest record was at 1414 m, south of the Charlie Gibbs Fracture Zone.
- We did not observe massive live reef structures, and the largest colony was approximately half a meter across. Remains of former large Lophelia-reefs were observed at several locations.

Orange roughy "resting" on corals (Lophelia pertusa or Solenosmilia variabilis).
The number of megafaunal species was higher in areas where corals dominated compared to areas without coral. Typical taxa that co-occurred with Lophelia were crinoids, certain sponges, the bivalve Acesta excavata, and squat lobsters.
- We observed signs of destructive fishing and lost fishing gear (gillnet and longline) at several locations, Mortensen says. Different possible reasons of the decease of these reefs such as climate change or destructive fisheries are discussed.

The study, which Mortensen made together with Lene Buhl-Mortensen (Institute of Marine Research, Norway), Andrey V. Gebruk and Elena M. Krylova (P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia ) will be published in the special issue of Deep-sea Research 2. This is dedicated to MAR-ECO related papers and will be out in 2007.

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