Journal article Open Access

Using novel acoustic and visual mapping tools to predict the small-scale spatial distribution of live biogenic reef framework in cold-water coral habitats

De Clippele, Laurence H; Gafeira, J; Robert, K; Hennige, S; Lavaleye, MS; Duineveld, GCA; Huvenne, VAI; Roberts, JM

Cold-water corals form substantial biogenic habitats on continental shelves and in deep-sea areas with topographic highs, such as banks and seamounts. In the Atlantic, many reef and mound complexes are engineered by Lophelia pertusa, the dominant framework-forming coral. In this study, a variety of mapping approaches were used at a range of scales to map the distribution of both cold-water coral habitats and individual coral colonies at the Mingulay Reef Complex (west Scotland). The new ArcGIS-based British Geological Survey (BGS) seabed mapping toolbox semi-automatically delineated over 500 Lophelia reef ‘mini-mounds’ from bathymetry data with 2-m resolution. The morphometric and acoustic characteristics of the mini-mounds were also automatically quantified and captured using this toolbox. Coral presence data were derived from high-definition remotely operated vehicle (ROV) records and high-resolution microbathymetry collected by a ROV-mounted multibeam echosounder. With a resolution of 0.35 × 0.35 m, the microbathymetry covers 0.6 km2 in the centre of the study area and allowed identification of individual live coral colonies in acoustic data for the first time. Maximum water depth, maximum rugosity, mean rugosity, bathymetric positioning index and maximum current speed were identified as the environmental variables that contributed most to the prediction of live coral presence. These variables were used to create a predictive map of the likelihood of presence of live cold-water coral colonies in the area of the Mingulay Reef Complex covered by the 2-m resolution data set. Predictive maps of live corals across the reef will be especially valuable for future long-term monitoring surveys, including those needed to understand the impacts of global climate change. This is the first study using the newly developed BGS seabed mapping toolbox and an ROV-based microbathymetric grid to explore the environmental variables that control coral growth on cold-water coral reefs.

Acknowledgements This study received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 678760 (ATLAS). This paper reflects the authors' alone view, and the European Union cannot be held responsible for any use that may be made of the information contained herein. The high-resolution ROV multibeam used in this study was gathered through the UK Ocean Acidification programme benthic consortium (NERC grant NE/H017305/1). We thank the captains and the crew of the RV Lough Foyle, RV Pelagia and RRS James Cook for assistance at sea and Juan Moreno Navas for providing modelled hydrodynamic data from the Mingulay Reef Complex. L. De Clippele was supported by the Heriot-Watt University James Watt studentship. J. Gafeira was funded by MAREMAP and publishes with permission of the Executive Director of The British Geological Survey (NERC). S. Hennige was funded by a NERC IRF (NE/K009028/1). V. Huvenne and K. Robert were funded by the ERC Starting Grant project CODEMAP (Grant no 258482) and the NERC MAREMAP Programme.
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