Soft corals assemblages in deep environments of the Menorca Channel (Western Mediterranean Sea)

Abstract

Image-based research in mesophotic and deep environments of the Mediterranean Sea has significantly increased during the past decades. So far, this research has been focused on the ecology of key structuring organisms such as scleractinians, antipatharians, gorgonians or large demosponges. However, the ecology of true soft corals has barely been studied and is still in a very preliminary stage. To overcome this situation, soft coral assemblages in shelf and slope environments of the Menorca Channel (Western Mediterranean Sea) have been studied through the quantitative analysis of 85 video transect recorded over 38500 m2. Highest soft coral diversity was encountered on the shelf edge, resembling deep Mediterranean gorgonian patterns. Three soft coral assemblages, segregated by depth, substrate, and slope were identified: two monospecific ones composed by Nidalia studeri and Alcyonium palmatum, respectively and a multispecific one composed by Paralcyonium spinulosum, Alcyonium sp., Chironephthya mediterranea and Daniela koreni. The evaluated species presented average densities within the same range as other deep Mediterranean anthozoans ranging from 1 to 9 col.·m−2. However, N. studeri and P. spinulosum punctually formed dense monospecific aggregations, reaching maximum densities of 49 col.·m−2 and 60 col.·m−2 respectively. Both species monopolized vast extensions of the continental shelf and shelf edge. The identification and ecological characterization of these assemblages brings new insight about deep Mediterranean anthozoan communities, and provides baseline for future management plans in the study area.