EFFECTS OF A MUCILAGE EVENT ON THE MEDITERRANEAN GORGONIAN PARAMURICEA-CLAVATA .1. SHORT-TERM IMPACTS AT THE POPULATION AND COLONY LEVELS

A Paramuricea clavata population thriving between 23 and 39 m depth on a shoal at the northern entrance to the Strait of Messina (Tyrrhenian Sea) was affected by mucilage coverage at the end of summer 1993. Muc ilage became entangled in projecting branches and necrotized the coene nchyme below, leaving the axial skeleton bare. The entire population w as heavily affected, extent of injuries being negatively correlated wi th size of colonies. Colony size, scale and location of damage were re lated to successful regeneration after six months. Smaller colonies sh owed a higher mortality, while colonies with over 50-60% of their tota l branch length damaged were overgrown by invaders and died. The exten t of injuries in the central part of the colony was found to be a crit ical parameter in determining colony regrowth. A number of injured col onies grew during the six months following the disappearance of mucila ge, which shows that their regrowth was apparently not influenced by s tress due to mucilage.