Mesophotic and Deep-Sea Vulnerable Coral Habitats of the Mediterranean Sea: Overview and Conservation Perspectives

Abstract

Although the different communities distributed in the mesophotic and deep waters play a fundamental role in the functioning of the marine ecosystems, the assessment of their global distribution is still far to be achieved. This is also true in the Mediterranean Sea, where exploration technologies are revealing a large diversity of unknown communities structured totally or partially by corals, which represent vulnerable marine ecosystems (VMEs) according to FAO's guidelines. This chapter aims to define and describe the main coral habitats of the mesophotic and aphotic zones of the Mediterranean, such as coralligenous formations, cold-water coral frameworks, coral forests and sea pen fields. The role of these habitats in providing benefit for a variety of invertebrates and fishes as well as a suite of ecosystem goods and services is highlighted. Fishing is one of the main anthropogenic impacts affecting Mediterranean coral habitats, and the current conservation measures are often ineffective. Ongoing attempts and future solutions aiming at the conservation of these VMEs are here discussed, including the fishing restriction in strategic areas characterized by lush coral communities, the implementation of controls against illegal fishery, the development of encounter protocols for vulnerable species and the use of observers onboard.

A mesophotic black coral forest in the Adriatic Sea

“…Marine explorations all over the Mediterranean Sea are revealing an exponential amount of coral communities from the mesophotic to the aphotic zones, highlighting how these extensive environments are still scantly explored, even in a well-studied basin as the Mediterranean 5,22 . Although Tremiti Islands are an MPA since 1989, the seabed below 50 m depth was completely unexplored and the presence of A. subpinnata was overall unknown.…”

“…These gears are considered fixed and less invasive compared to trawl nets but, although static on the seabed, they may be pulled across the bottom for short distances by strong currents or during retrieval operations. For this reason, they represent destructive fishing gears for three-dimensional benthic organisms, showing a significant mechanical impact on VME indicator taxa such as corals, and their use should be banned from areas characterized by coral forests 5 .…”

“…Their name comes from the Greek "anti pàthos", literally "against suffering", because these rare corals were used in the past for medical purposes or to make amulets against illnesses and, currently, some antipatharian species are still used in the jewellery industry. Black corals often live as isolated colonies but, under proper conditions, they can form dense aggregations that belong to the so-called "coral forests" or "coral gardens" [2][3][4][5] , representing Vulnerable Marine Ecosystems (VMEs). These forests can be monospecific or can consist of a combination of coral species constituting complex communities that can include both hexacorals and octocorals 6 .…”

Size/Age Models for Monitoring of the Pink Sea Fan Eunicella verrucosa (Cnidaria: Alcyonacea) and a Case Study Application

“…In fact, the exclusion of demersal towed equipment has benefited E. verrucosa populations and other benthic taxa in the Lyme Bay Marine Protected Area (MPA; southwest England) [44], emphasizing the role of MPAs for the conservation of vulnerable and threatened species. However, bottom longlines and artisanal fishing nets (e.g., trammel nets and gillnets), often considered of scarce impact on benthic communities, also have a relevant bycatch rate on mesophotic and deep-sea coral species [24,45,46]. These gears can have a significant impact on E. verrucosa, as they can bycatch the colonies during fishing operations, but also lost fishing gears can be entangled in the colonies and damage them (ghost fishing) [5,23].…”

Identifying Priorities for the Protection of Deep Mediterranean Sea Ecosystems Through an Integrated Approach

“…While the basin is traditionally considered one of the most intensively investigated areas of the world in both terrestrial and coastal marine biodiversity, it lags other regions of the world in studies of its deep-sea fauna (Danovaro et al, 2010). However, the Mediterranean sea is a hot spot of biodiversity with a uniquely high percentage of endemic species (Myers et al, 2000), and despite its small dimensions (0.82% of the ocean surface), it hosts more than 7.5% of global biodiversity (Bianchi and Morri, 2000) with several unique and rare ecosystems occurring in its deeper part (Chimienti et al, 2020).…”