Gorgonian corals are long-lived, slow-growing species exhibiting slow population dynamics. Demographic data collected over a period of 11 yr on a small population of temperate, canopyforming gorgonians dwelling near the edge of the summer thermocline in the northwestern Mediterranean Sea enabled us to assess its responses to the large mortality events that occurred in 1999 and 2003. Changes in population density, size structure and recruitment were examined. Overall, 2101 adult colonies and recruits were observed in situ and 240 photographic plots analyzed. During the first 3 years (2004 to 2006) after the mass mortalities, our measurements revealed a dramatic reduction in the density of healthy colonies (90% suffered total or partial mortality), a shift in the dominant size class towards smaller size and a significant reduction in recruitment. In the following years (2007 to 2008) a significant recovery of injured colonies was found, with almost complete detachment of the dead colonies, a reduction in mortality and a 4-fold increase in recruitment. These findings indicate clear-cut restoration trends of the population, suggesting that recovery after extensive mortality could be faster than predicted by our current knowledge of gorgonian population dynamics. © Inter-Research 2009.

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