New contribution on the distribution and ecology of Dendrophyllia ramea (Linnaeus, 1758): abundance hotspots off north‐eastern Sicilian waters

Abstract

Dendrophyllia ramea is a poorly known arborescent scleractinian coral, whose worldwide distribution is limited to the southern part of the Mediterranean basin, and to the Atlantic Ocean between Macaronesia and Gulf of Cadiz. The geographical distribution and abundance of D. ramea were herein updated, considering a total of 19 records, seven of which have never previously been reported in scientific papers. Between 2010 and 2017, five Remotely Operative Vehicle surveys carried out along the Sicilian coast recorded 89 colonies. No exhaustive data on density and ecology of this species have been published to date. Data for two areas off the north‐eastern Sicilian waters (Aeolian Island and Gulf of Patti) are reported, including the species’ bathymetric distribution, abundance, population density, colony morphometry, population size structure and surrounding habitat description. Size structure and density of D. ramea populations were compared with lost fishing gear density. Around the Aeolian Islands, where little lost fishing gear was observed, the D. ramea population was denser compared with the populations at two sites within the Gulf of Patti, where a greater amount of lost fishing gear was observed. The analysis of D. ramea size classes (single corallite, 2–5 polyps, >5 polyps) at different sites showed that impact varied with fishing gear typology: while lines damage the branches of larger colonies, nets can completely remove them. The limited distribution of D. ramea in some areas also makes this species very vulnerable to impacts such as changes in the chemical–physical characteristics and circulation of sea water. Dendrophyllia ramea is classified as ‘Vulnerable’ according to the Mediterranean IUCN Red List, and it is listed in the Barcelona Convention (Annex B). Data on the distribution of D. ramea allows us to review the species’ classification and propose that its status be changed to ‘Endangered’.

A Dendrophyllia ramea Population in the Ionian Sea (Central Mediterranean Sea) Threatened by Anthropogenic Impacts

“…Smaller colonies formed patches at higher densities. These results are comparable with those recently obtained by Orejas et al (2017), while they are higher than those reported by Salvati et al (2021) for northern Sicily.…”

“…In the study area, this species thrives on boulders on a sedimentary plateau at 70-80 m depth, as described by several authors in other Mediterranean areas (Zibrowius, 1980;Aguilar et al, 2006;Templado et al, 2009). Moreover, the bathymetric range is similar to that observed by Salvati et al (2021) in northern Sicily. Some isolated D. ramea corallites were also observed on the soft substratum (Figure 3D) between boulders.…”

“…However, colonies growing directly on the soft bottom, as described by Orejas et al (2017), were not recorded. This species inhabits different geomorphologic settings, all characterized by highly dynamic systems (Salvati et al, 2021). The peculiar characteristic of the Ionian Sea in the dynamics and processes of water exchange, important in determining biological patterns (Bonanno et al, 2006;Bergamasco and Malanotte-Rizzoli, 2010;Celentano et al, 2020), could support the flourishing settlement of D. ramea in this area.…”

“…In the Mediterranean, this species has been reported mainly in the southern basin with a patchy distribution, and it is considered rare (Orejas et al, 2019a). Recently, Salvati et al (2021) updated the D. ramea Mediterranean distribution with new records from northeastern Sicily. In this basin, D. ramea generally developed in the circalittoral zone on rocky substratum or bioconstruction characterized by moderate currents and turbidity, usually between 40 and 80 m depth, up to the maximum recorded depth of ∼240 m (Bonfitto et al, 1994;Jiménez et al, 2016;Orejas et al, 2017).…”

“…It is known for its use for ornamental purposes in both the Mediterranean Sea and the Atlantic Ocean. Moreover, it is affected by bycatch and entanglement in lost fishing gear (Salvati et al, 2021). For these reasons, it is listed as Vulnerable in the Mediterranean Red List (Anthozoans) (Otero et al, 2017) of the International Union for the Conservation of Nature (IUCN) and as Data Deficient in the Italian IUCN Red List (Italian corals) (Salvati et al, 2014).…”