Long-term recruitment of soft-corals (Octocorallia: Alcyonacea) on artificial substrata at Eilat (Red Sea)

Abstract

Recruitment of soft corals (Octocorallia: Alcyonacea) on concrete plates was studied in the reefs of the Nature Reserve of Eilat at depths of 17 to 29 m over 12 yr. Xenia macrospiculata was the pioneering species, appealing on the vast majority of the plates before any other spat. This species remained the most conspicuous inhabitant of the substrata throughout the whole study. Approximately 10 % of the plates were very extensively colonized by X. rnacrospiculata, resembling the percentage of living coverage by the species in the surrounding reef, thus suggesting that during the study X. rnacrospiculata populations reached their maximal potential to capture the newly available substrata. The successive appearance of an additional 11 soft coral species was recorded. The species composition of the recruits and their abundance corresponded with the soft coral community in the natural reef, indicahng that the estabhshed spat were progeny of the local populations. Soft coral recruits utilized the edges and lower surfaces of the plates most successfully, rather than the exposed upper surfaces. Such preferential settling of alcyonaceans allows the spat to escape from unfavourable conditions and maintains their high survival in the established community.