Effects of massive macroalgal epibiosis on the red gorgonian Paramuricea clavata (Cnidaria, Anthozoa)

This study reports the massive overgrowth of macroalgae on living colonies of the red gorgonian Paramuricea clavata at Tremiti Islands Marine Protected Area (Adriatic Sea). Colonies density was reduced of 40-50% on both the top and the slope of the studied shoal from 2014 to 2019, and the P. clavata population was severely covered by the erect macroalgae Sporochnus pedunculatus and Pylaiella littoralis. Although the causes of such unusual phenomenon needs to be assessed, it is hypothesized that the increasing of water temperature and the occurrence of massive and persistent benthic mucilaginous blooms registered in these years could have severely stressed the gorgonians, increasing their vulnerability to algal epibionts.