The “Corsica Channel Cold-Water Coral Province” (Mediterranean Sea)

Lorenzo Angeletti,Marco Taviani,Giorgio Castellan,Paolo Montagna,Alessandro Remia

doi:10.3389/fmars.2020.00661

Abstract

Over 25 mounds have been identified in the Corsica Channel (Mediterranean Sea) through multibeam bathymetric mapping at depth of 400-430 m, with dimensions ranging from 70 to 330 m, achieving maximum heights of 25 m. Two such mounds were explored in detail by means of Remotely Operated Vehicle, revealing thick coral growth with a predominance of the branching scleractinian Madrepora oculata as main frame-builder, and subordinate Desmophyllum pertusum. The solitary species Desmophyllum dianthus and Javania cailleti add to the biodiversity here, which accounts for at least 50 macro- and megabenthic species. In consideration of the remarkable surface (ca. 3.4 km2) covered by living corals, their density and healthy appearance, and discontinuity with other major CWC occurrences in the Mediterranean Sea, we propose that this area represents a distinct CWC province in a sector already known for the presence of pre-modern CWC mounds. Noticeably, well-developed contourite drift systems occur in the Corsica Channel, lending support to their strict link with coral establishment at depth. The ecosystemic value of the new CWC province calls for proper conservation measures to ensure their present Good Environmental Status.

Highlights

The concept of “Cold-Water Coral Province” is not rigorously codified in literature far, vaguely referring by convention to geographically discrete areas with important deep-sea scleractinian presence (e.g., Taviani et al, 2011; Hebbeln et al, 2014; Mohn et al, 2014; Wienberg et al, 2018)
There is a consolidated consensus that cold-water coral (CWC) establish under a bottom current regime of high intensity, with the Levantine Intermediate Water (LIW) mass as the main driver controlling their distribution in the Mediterranean Basin (Freiwald et al, 2009; Taviani et al, 2016, 2017; Orejas and Jiménez, 2019)
Exploration of the southern Ligurian and northern Tyrrhenian seas in the frame of the Italian Marine Strategy Framework Directive in 2016 and 2017 documented in the present study proves prolonged CWC regional presence, not necessarily continuous

Summary

Introduction

The concept of “Cold-Water Coral Province” is not rigorously codified in literature far, vaguely referring by convention to geographically discrete areas with important deep-sea scleractinian presence (e.g., Taviani et al, 2011; Hebbeln et al, 2014; Mohn et al, 2014; Wienberg et al, 2018). It is anyhow of practical use because (i) it identifies those situations where the area covered by cold (or deep)-water corals (CWCs) is often many tens square kilometers, far exceeding occasional to sparse CWC occurrences; and (ii) it helps to narrow the areal of seabed meritorious of special attention for management and protection purposes. Along the LIW path, the recent visual surveys have, led to the discovery of healthy CWC grounds in the Nora and Dorhn canyons in the Tyrrhenian Sea (Taviani et al, 2017, 2019)

Methods

Results

Conclusion