Report | October 31, 2014
Vulnerable habitats and species in the deep-sea Emile Baudot escarpment (South Balearic Islands) surveyed by ROV
Abstract
Geological features like seamounts and canyons are known to be potential biodiversity hotspots due to the variety of bathymetric ranges, substrata, habitats and species that they can host. Escarpments share these characteristics and new findings show they can be considered as important biological hotspots. Remotely operated vehicle (ROV) dives between 100 and 1000 m depth carried out in the Emile Baudot Escarpment (Southern Balearic Islands) and the surrounding shelf-break have provided new data on the distribution of deep-sea habitats and species. The most important factor influencing species and habitats’ presence is the nature of the substrate and the bathymetry. Although most of the area is heavily covered by sediment, rocky outcrops and overhangs show thanatocenoses of oysters and corals. Coral framework and oyster shells are colonized by other cnidarians, mollusks and sponges like Caryophyllia calveri, Spondylus gussonii or Tretodyctium tubulosum. Some Neopycnodonte zibrowii individuals can even still be found alive. Important aggregations and communities of the crinoid Leptometra phalangium and the brachiopod Gryphus vitreus occupy a wide area on the shelf-break and on top of the escarpment. Different researches and international fora (like UNEP or FAO) include these communities in the classification of vulnerable, sensitive or essential habitats and ecosystems.
Introduction
Emile Baudot is the largest escarpment in the Western Mediterranean, stretching up to 275 kilometers long. It is SW-NE oriented, with depths ranging from 200 m in the shallowest part to deeper than 2,000 m at its base (Acosta et al., 2002). It splits the Western basin into two regions: the Balearic Sea in the North and the Algerian Basin in the South. The Northeastern area of the escarpment has sharper gradients and is highly covered by sediments, while the Southwestern flank is dotted by different submarine elevations and the lower sediment deposition allows rocks to emerge. The escarpment concentrates a wide array of geomorphological features including guyots, seamounts, submarine canyons, underwater cliffs, volcanic pinnacles, etc. (Acosta et al., 2001; 2004). ROV dives have provided images of the biological communities present over soft and hard bottoms, giving a first overview of the species and habitats´ distribution range. The geodiversity in this deep-sea area allows the proper settlement of peculiar species and the occurrence of ecologically important habitats
