Cold‐water coral assemblages on vertical walls from the Northeast Atlantic

Katleen Robert,Veerle A I Huvenne,Aggeliki Georgiopoulou,Daniel O B Jones,K C Burns

doi:10.1111/ddi.13011

Abstract

AbstractAimIn this study, we assess patterns of cold‐water coral assemblages observed on deep‐sea vertical walls. Similar to their shallow‐water counterparts, vertical and overhanging walls in the deep sea can host highly diverse communities, but because of their geometry, these habitats are generally overlooked and remain poorly known. These vertical habitats are however of particular interest, because they can protect vulnerable coral ecosystems from trawling activities. As such, it is important to understand their ecology and assess their global importance.LocationVertical walls on complex geomorphic features, in particular walls of the Rockall Bank Slope Failure Escarpment, Whittard and Explorer Canyons, Northeast Atlantic.MethodsVideo analysis of remotely operated vehicle transects carried out at five sites is used to investigate differences in species composition and diversity across walls and to compare those to nearby cold‐water coral sites on flat terrain. A high‐resolution photogrammetric reconstruction is further employed to examine whether wall complexity plays a role in promoting niche differentiation at very fine spatial scales.ResultsThe investigated walls showed differences in species assemblage both across walls and in comparison to flat sites, with the fine‐scale heterogeneity engendered by walls allowing niche differentiation between closely related taxa.Main ConclusionsVertical walls represent an important cold‐water coral habitat with differences in species composition across walls within a region, illustrating their role in driving diversity patterns. Based on publicly available bathymetric datasets and a catalogue of broad‐scale terrain features, globally over 8,000 features are likely to have vertical walls and cold‐water corals, which highlight the need to consider deep‐sea vertical habitats in current conservation efforts.

Highlights

In order to address conservation needs in the deep sea, we need to understand better the spatial distribution of ecologically important habitats, and this can be facilitated by identifying the factors that play significant roles in shaping biological spatial patterns
To further establish how vertical walls may provide different habitats, we investigated the spatial distribution of three Alcyonacea species at local scales
Differences in habitat use between certain species were demonstrated at the scale of a single wall, with the fine-scale structural complexity provided by vertical habitats likely providing additional niche space exploited by certain species

Summary

Introduction

In order to address conservation needs in the deep sea, we need to understand better the spatial distribution of ecologically important habitats, and this can be facilitated by identifying the factors that play significant roles in shaping biological spatial patterns. Niche theory suggests that each species exploits its environment differently (i.e., niche differentiation) and communities arise from heterogeneity in environmental conditions and limited resources (Hutchinson, 1957). This hypothesis implies that more complex environments, which provide increased niche differentiation, may act as biodiversity hotspots of particular conservation value. The main issue in the deep sea is that most habitats are poorly studied, with rarer ones still being discovered

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