A catastrophic mass-mortality episode of gorgonians and other organisms inthe Ligurian Sea (Northwestern Mediterranean), summer 1999

In the late summer of 1999, an extensive mortality of gorgonians and other epi benthic organisms was observed in the Ligurian Sea (Mediterranean Sea) from the Tuscan Archipelago to Marseille. Quantitative data from Tino Islan d and Portofino Promontory indicated that the proportion of affected gorgon ians ranged from 60% to 100% in populations having a density of 9-27.8 colo nies m(-2), suggesting that millions of sea fans died along the coast of Li guria. This mass mortality episode coincided with a sudden increase of sea water temperature down to more than 50 m depth. Laboratory analyses showed that the colonies stressed by high temperature also underwent extensive att ack by microrganisms (protozoans and fungi), which are interpreted as oppor tunistic pathogens.