Sneaking into a Hotspot of Biodiversity: Coverage and Integrity of a Rhodolith Bed in the Strait of Sicily (Central Mediterranean Sea)

Abstract

Habitat mapping, physical characteristics and benthic community of a rhodolith bed in the Pelagie Islands (Strait of Sicily, Mediterranean Sea) were studied through Multi–Beam Echo–Sounder (MBES), Remotely Operated Vehicle (ROV) and grab samples. The geomorphological analysis revealed an articulated and wide rhodolith bed; video inspections highlighted a bed with high coverage, few sandy patches and with a prevalence of the boxwork morphotype. A total of 207 taxa with 876 specimens were identified, and Polychaeta was the dominant taxon. Linguimaera caesaris, a Lessepsian benthic amphipod, was recorded in all sampling sites, and its presence represents an input to deepen the benthic assemblage research on the rhodolith bed. In terms of morphotype composition, dead/live ratio and species variability, the bed variability indicated a good status of health, although trawling signs were detected through ROV videos. The present study broadens the knowledge on Mediterranean rhodolith beds and supports the importance of survey and monitoring activities for the conservation and management of this important habitat.

Habitat characterization, anthropogenic impacts and conservation of rhodolith beds off southeastern Malta

“…A much larger rhodolith bed (918 km 2 ) is present in the Menorca Channel (Barberá et al, 2012). Significantly smaller rhodolith beds, covering areas of <10 km 2 in Tabarca (Spain), Campania and Apulia (Italy) (Bordehore et al, 2003; Chimienti et al, 2020; Rendina et al, 2020), and of 20–41 km 2 in northeast Malta, Lampedusa and Sardinia (Bracchi et al, 2022; Maggio et al, 2022; Sciberras et al, 2009), occur elsewhere in the Mediterranean. The Maltese and Menorcan beds are also large at a European scale, since most rhodolith beds recorded from the north‐western Atlantic are smaller than 50 km 2 (Hall‐Spencer et al, 2010; Jardim et al, 2022; Neves et al, 2021).…”

“…Rhodolith cover reached a peak of 74% but was more often found at <50%, which is comparable with findings from the Spanish coast, Sardinia, Campania and Apulia, where maximum values ranged between 43% and 66% (Bracchi et al, 2022; Chimienti et al, 2020; Illa‐López et al, 2023; Rendina et al, 2020). An even denser bed, with >87% rhodolith cover, occurs in Lampedusa (Maggio et al, 2022).…”

“…Rhodolith beds are known to support a high diversity of associated fauna, including macroalgae, epifauna and infauna, as well as fish (Moura et al, 2021; Nelson et al, 2014; Neves & Costa, 2022). In the Mediterranean, crustaceans, polychaetes and sometimes molluscs are the main contributors to faunal diversity (Bordehore et al, 2003; Deidun et al, 2022; Maggio et al, 2022; Sciberras et al, 2009). Sponges, cnidarians, echinoderms and fishes had the highest number of species in the present study, but these results are not directly comparable to those of other studies, given that the latter mainly focused on macrobiota collected through grab sampling, in contrast to the visual observation of megabiota in ROV footage used here.…”

“…In the Mediterranean, crustaceans, polychaetes and sometimes molluscs are the main contributors to faunal diversity (Bordehore et al, 2003;Deidun et al, 2022;Maggio et al, 2022;Sciberras et al, 2009). Sponges, cnidarians, echinoderms and fishes had the highest number of species in the present study, but these results are not directly comparable to those of other studies, given that the latter mainly focused on macrobiota collected through grab sampling, in A rather impoverished non-coralline algal diversity was recorded from the southeast Malta rhodolith bed, dominated by Flabellia petiolata followed by Zonaria tournefortii, mirroring the current situation on the bed off the northeastern coast of Malta (Deidun et al, 2022).…”

Non‐extractive fish diversity assessment in Mediterranean rhodolith beds

“…In the Mediterranean, the distribution and conservation status of rhodolith beds are still poorly known, hindering the implementation of adequate conservation plans, although advances have been made in some locations (e.g., Barberá et al, 2012; Maggio et al, 2022; Romagnoli et al, 2021; Sciberras et al, 2009). In this context, identifying and monitoring rhodolith beds that are in good ecological condition is urgent.…”