Diseases affect cold-water corals too: Eunicella verrucosa (Cnidaria : Gorgonacea) necrosis in SW England

Abstract

The first recorded incidence of cold-water coral disease was noted in Eunicella verrucosa, a coral on the international 'red list' of threatened species, at a marine protected area in SW England in 2002. Video surveys of 634 separate colonies at 13 sites revealed that disease outbreaks were widespread in SW England from 2003 to 2006. Coenchyme became necrotic in diseased specimens, leading to tissue sloughing and exposing skeletal gorgonin to settlement by fouling 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.