Abstract
In this study, we mapped the distribution of Cold-Water Coral (CWC) habitats on the northern Ionian Margin (Mediterranean Sea), with an emphasis on assessing coral coverage at various spatial scales over an area of 2,000 km2 between 120 and 1,400 m of water depth. Our work made use of a set of data obtained from ship-based research surveys. Multi-scale seafloor mapping data, video inspections, and previous results from sediment samples were integrated and analyzed using Geographic Information System (GIS)-based tools. Results obtained from the application of spatial and textural analytical techniques to acoustic meso-scale maps (i.e. a Digital Terrain Model (DTM) of the seafloor at a 40 m grid cell size and associated terrain parameters) and large-scale maps (i.e. Side-Scan Sonar (SSS) mosaics of 1 m in resolution ground-truthed using underwater video observations) were integrated and revealed that, at the meso-scale level, the main morphological pattern (i.e. the aggregation of mound-like features) associated with CWC habitat occurrences was widespread over a total area of 600 km2. Single coral mounds were isolated from the DTM and represented the geomorphic proxies used to model coral distributions within the investigated area. Coral mounds spanned a total area of 68 km2 where different coral facies (characterized using video analyses and mapped on SSS mosaics) represent the dominant macro-habitat. We also mapped and classified anthropogenic threats that were identifiable within the examined videos, and, here, discuss their relationship to the mapped distribution of coral habitats and mounds. The combined results (from multi-scale habitat mapping and observations of the distribution of anthropogenic threats) provide the first quantitative assessment of CWC coverage for a Mediterranean province and document the relevant role of seafloor geomorphology in influencing habitat vulnerability to different types of human pressures.
Highlights
Cold-Water Coral (CWC) habitats form one of the most Vulnerable Marine Ecosystems (VME) to human pressures within the deep sea [1,2,3]
Terrain analyses on the obtained Digital Terrain Model (DTM) were focused on quantitatively outlining the blocky pattern within which the coral mounds are densely distributed
A semi-automatic morphometric feature extraction was performed over the computed Terrain Morphometric Attributes (TMAs) in order to, as follows: (1) Outline the blocky pattern that is 600 km2 in area and that extends over the entire investigated sector of the northern Ionian Margin (Figure 6a)
Summary
Cold-Water Coral (CWC) habitats form one of the most Vulnerable Marine Ecosystems (VME) to human pressures within the deep sea [1,2,3]. With the rise of human activity within the deep sea, such habitats are under increasing pressure from a number of different [14,15], synergetic [3], and cumulative threats [16] (e.g. pollution and litter, aggregate mining, oil and gas exploration, coastal development, cables, shipping, invasive species, climate change, etc.). Many of these threats are common to all deep-sea habitats and fauna it is still not clear how a given deep-sea habitat can be differentially impacted by each, and how their synergetic impacts vary according to habitat structure. European research (for example, MESH (http://www.searchmesh.net/), MAREANO (http://www.mareano.no/), EU-FP6 HERMES (http:// www.eu-hermes.net/), EU-FP7 HERMIONE (http://www.euhermione.net/), and EU-FP7 CoralFISH (http://www.eu-fp7coralfish.net/)) and government-supported projects have recently included suitable benthic habitat maps for Atlantic waters
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