A unique and threatened deep water coral-bivalve biotope new to the Mediterranean Sea offshore the Naples megalopolis

Marco Taviani,Lorenzo Angeletti,Paolo Montagna,Roberto Danovaro,Frine Cardone

doi:10.1038/s41598-019-39655-8

Abstract

The Gulf of Naples is an example of the most beautiful and biodiverse marine regions of the Mediterranean Sea and of the most impacted areas in terms of industrial activities, large contaminated areas, resource exploitation, infrastructures at sea and maritime transportation. We conducted Remotely Operated Vehicle surveys in the Dohrn Canyon in the Tyrrhenian Sea at approximately 12 NM off Naples metropolitan area, and revealed a hotspot of deep-sea benthic biodiversity of sessile fauna at ca. 400 m depth. The hard bottoms are characterized by a high abundance of charismatic species, such as the habitat forming cold-water corals (CWC) Madrepora oculata, Lophelia pertusa, Desmophyllum dianthus in association with the large size bivalves Acesta excavata and Neopycnodonte zibrowii. This CWC-bivalve co-occurrence represents a novel biotope for the Mediterranean Sea, which coexists with the evidence of severe anthropogenic threats, such as illegal dumping and fishery malpractices that were visually documented during the survey. We recommend the adoption of specific protection measures to preserve these unique deep-sea assemblages showing the uncommon co-existence of such a number of deep-sea species in a single habitat.

Highlights

In the 19th century, the beauty and biological richness of the Gulf of Naples (GoN) was such to convince Anton Dohrn to found there in 1872 the first marine station in the world to demonstrate the validity of the Darwin theories on evolution using marine organisms
Other water masses can be recognized within the GoN, such as the Tyrrhenian Intermediate Water (TIW) formed during winter mixing at depths down to ~150 m and the Tyrrhenian Surface Water (TSW) found above 75 m as the result of summer warming and freshening of the TIW20
From what observed so far in the Mediterranean Sea, where cold-water coral habitats are predominantly characterized by M. oculata, in the Dohrn Canyon L. pertusa is the most abundant species, especially on the northwestern flank where as many as 10 colonies of each species have been counted on a distance of 235 m between 375–455 m water depth

Summary

Introduction

In the 19th century, the beauty and biological richness of the Gulf of Naples (GoN) was such to convince Anton Dohrn to found there in 1872 the first marine station in the world to demonstrate the validity of the Darwin theories on evolution using marine organisms. Despite a long tradition of biological studies that renders the GoN one of the most intensively investigated marine areas of the world, little is known about the ecology and environmental status of the deep-sea habitats of the gulf, whose hard bottom has been so far investigated only in terms of geological setting. −250 m and sharply declining down to ca 1300 m in the Tyrrhenian plain[14,15] This inactive canyon, part of the Magnaghi-Dohrn canyon system[16] and consisting of a western and an eastern branch, is thought to have been formed in response to relative www.nature.com/scientificreports/. The survey unveiled for the first time the presence of charismatic benthic life in the canyon system, with biological traits previously unreported for the entire Mediterranean basin

Methods

Results

Conclusion