Global habitat suitability of cold‐water octocorals

Abstract

Aim Three‐quarters of Octocorallia species are found in deep waters. These cold‐water octocoral colonies can form a major constituent of structurally complex habitats. The global distribution and the habitat requirements of deep‐sea octocorals are poorly understood given the expense and difficulties of sampling at depth. Habitat suitability models are useful tools to extrapolate distributions and provide an understanding of ecological requirements. Here, we present global habitat suitability models and distribution maps for seven suborders of Octocorallia: Alcyoniina, Calcaxonia, Holaxonia, Scleraxonia, Sessiliflorae, Stolonifera and Subselliflorae. Location Global. Methods We use maximum entropy modelling to predict octocoral distribution using a database of 12,508 geolocated octocoral specimens and 32 environmental grids resampled to 30 arc‐second (approximately 1 km2) resolution. Additionally, a meta‐analysis determined habitat preferences and niche overlap between the different suborders of octocorals. Results Suborder Sessiliflorae had the widest potential habitat range, but all records for all suborders implied a habitat preference for continental shelves and margins, particularly the North and West Atlantic and Western Pacific Rim. Temperature, salinity, broad scale slope, productivity, oxygen and calcite saturation state were identified as important factors for determining habitat suitability. Less than 3% of octocoral records were found in waters undersaturated for calcite, but this result is affected by a shallow‐water sampling bias. Main conclusions The logistical difficulties, expense and vast areas associated with deep‐sea sampling leads to a gap in the knowledge of faunal distributions that is difficult to fill without predictive modelling. Global distribution estimates are presented, highlighting many suitable areas which have yet to be studied. We suggest that approximately 17% of oceans are suitable for at least one suborder but 3.5% may be suitable for all seven. This is the first global habitat suitability modelling study on the distribution of octocorals and forms a useful resource for researchers, managers and conservationists.

In-situ observation of deep water corals in the northern Red Sea waters of Saudi Arabia

“…DWCs are usually occur in areas of pronounced topographic relief and their distribution and abundance are influenced by environmental factors such as temperature, water current and substrate type (Mortensen and Buhl-Mortensen, 2004;Buhl-Mortensen et al, 2010;Guinan et al, 2009;Yesson et al, 2012;Bryan and Metaxas, 2006;Tong et al, 2012;Rengstorf et al, 2013). In our study, the maximum abundance and diversity of DWC was recorded from an area (A1) that is located relatively near the shore (Fig.…”

“…Among the 723 azooxanthellate scleractinian coral species currently known, the majority (532 species, 73.6%) are solitary in habit while the remainder (191,26.4%) are colonial. The distribution of DWC is governed by various factors including temperature and calcium carbonate saturation (Cairns, 2007), topographic relief (Mortensen and Buhl-Mortensen, 2004;Buhl-Mortensen et al, 2010;Guinan et al, 2009;Yesson et al, 2012), sedimentary regime and currents (Thiem et al, 2006;Bryan and Metaxas, 2006;Wilson et al, 2007;Dolan et al, 2008).…”

Cold-Water Coral Habitats in Submarine Canyons of the Bay of Biscay

“…The size of coral habitats, of which most segments measured less than 100 m, compared to the resolution of the environmental factors, ranging from 100 m to 0.083 • latitude (∼10 km) easily explain the difficulty to discriminate particular environmental settings for the different coral habitats. The observed pattern also points out the limits of habitat suitability models which were based on a rather low resolution of oceanographic parameters (0.04 • -1 • latitude) (Davies et al, 2008;Davies and Guinotte, 2011;Yesson et al, 2012). Limited resolution understandably causes uncertainties in habitat mapping and suitability models (Davies and Guinotte, 2011;Rengstorf et al, 2012) whereby some local features, such as individual coral habitats, could be missed.…”

“…Terrain parameters can be extracted from multibeam bathymetry and can serve as useful surrogates for habitat mapping. Slope, rugosity and Bathymetric Position Index (BPI) are examples of parameters measuring canyon topography and are known to have an influence on the presence of CWC species/habitats (e.g., Howell et al, 2011;Yesson et al, 2012;Robert et al, 2015).…”

Major impacts of climate change on deep-sea benthic ecosystems

“…This degradation could have implications for habitat provision with consequent effects on fish populations and fisheries production. Likely major impact zones include CWC reefs found in the northern Atlantic and Arctic Oceans, the Southern Ocean, and around New Zealand (Guinotte et al, 2006;Yesson et al, 2012) where deep-water pH could decrease by approximately 0.3-0.4 pH units by 2100 relative to current day values. Reduced food supply owing to lower POC fluxes could exacerbate these impacts because the metabolic cost of increased rates of calcification become greater as pH declines (Wood et al, 2008).…”