Rare British coral struck by disease

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British scientists have recorded the first incidence of a coldwater coral disease in a species on an international list of threatened species.

Experts from the Marine Institute at the University of Plymouth recorded the disease in the Pink sea fan, Eunicella verrucosa, in a marine protected area in south west England.

The Pink sea fan, which is a type of gorgonian, is protected under Schedule 5 of the Wildlife and Countryside Act and is listed as vulnerable on the IUCN Red List of threatened species.

According to the study, which is published in the latest volume of the journal Diseases of Aquatic Organisms, video surveys of 634 colonies at 13 sites have suggested that the disease has been widespread across south west England between 2003 and 2006.

The authors said that affected corals had necrotic coenchyme, which led to them sloughing tissue and exposing their skeletal gorgonin, which became fouled by other marine organisms.

"Sites where necrosis was found had significantly higher incidences of fouling. No fungi were isolated from diseased or healthy tissue, but significantly higher concentrations of bacteria occurred in diseased specimens.

"Of 21 distinct bacteria isolated from diseased tissues, 19 were Vibrionaceae, 15 were strains of Vibrio splendidus and 2 others closely matched Vibrio tasmaniensis.

"Vibrios isolated from E. verrucosa did not induce disease at 15 degrees C, but, at 20 degrees C, controls remained healthy and test gorgonians became diseased, regardless of whether vibrios were isolated from diseased or healthy colonies.

"Bacteria associated with diseased tissue produced proteolytic and cytolytic enzymes that damaged E. verrucosa tissue and may be responsible for the necrosis observed.

"Monitoring at the site where the disease was first noted showed new gorgonian recruitment from 2003 to 2006; some individuals had died and become completely overgrown, whereas others had continued to grow around a dead central area."

The species became threatened by collection for the souvenir trade during the 1960s. Fishing nets and potting, scuba diver damage and smothering by other organisms are also believed to have played a part in the decline of the species.

For more information see the paper: Hall-Spencer JM, Pike J, Munn CB (2007) - Diseases affect cold-water corals too: Eunicella verrucosa (Cnidaria: Gorgonacea) necrosis in SW England. Dis Aquat Organ. 2007 Jun 29;76(2):87-97.