Distribution of deep-water scleractinian and stylasterid corals across abiotic environmental gradients on three seamounts in the Anegada Passage

Abstract

In the Caribbean Basin the distribution and diversity patterns of deep-sea scleractinian corals and stylasterid hydrocorals are poorly known compared to their shallow-water relatives. In this study, we examined species distribution and community assembly patterns of scleractinian and stylasterid corals on three high-profile seamounts within the Anegada Passage, a deep-water throughway linking the Caribbean Sea and western North Atlantic. Using remotely operated vehicle surveys conducted on the E/V Nautilus by the ROV Hercules in 2014, we characterized coral assemblages and seawater environmental variables between 162 and 2,157 m on Dog Seamount, Conrad Seamount, and Noroît Seamount. In all, 13 morphospecies of scleractinian and stylasterid corals were identified from video with stylasterids being numerically more abundant than both colonial and solitary scleractinians. Cosmopolitan framework-forming species including Madrepora oculata and Solenosmilia variabilis were present but occurred in patchy distributions among the three seamounts. Framework-forming species occurred at or above the depth of the aragonite saturation horizon with stylasterid hydrocorals being the only coral taxon observed below Ωarag values of 1. Coral assemblage variation was found to be strongly associated with depth and aragonite saturation state, while other environmental variables exerted less influence. This study enhances our understanding of the factors that regulate scleractinian and stylasterid coral distribution in an underreported marginal sea and establishes a baseline for monitoring future environmental changes due to ocean acidification and deoxygenation in the tropical western Atlantic.

Phylogeography of Paramuricea: The Role of Depth and Water Mass in the Evolution and Distribution of Deep-Sea Corals

“…Still, the rate of change of most variables (except for pressure) depends on geographic location. Several of these properties (e.g., temperature, salinity, oxygen) are linked directly to water mass structure, which has implications for controlling biogeographic patterns (see Auscavitch et al, 2020;Puerta et al, 2020;Roberts et al, 2021). For example, water masses that move across ocean basins might promote larval dispersal while the density interfaces between them might constrain dispersal Quattrini et al, 2017;Bracco et al, 2019).…”

Stylasterid corals build aragonite skeletons in undersaturated water despite low pH at the site of calcification

“…Stylasterids on the other hand, while not the first aragonitic taxon to exhibit low skeletal δ 11 B (e.g. H. elegans ), are the first to show this feature whilst living at depths close to and below the carbonate saturation horizon 36 . Assuming that stylasterid δ 11 B reflects the pH of the CF according to the abiotic relationship between the borate ion and pH (Eq.…”

Identifying Black Corals and Octocorals From Deep-Sea Imagery for Ecological Assessments: Trade-Offs Between Morphology and Taxonomy

“…Advancements in camera technology and imaging platforms have also facilitated the acquisition of higher quality imagery, enabling more accurate species identification (Durden et al, 2016;Schoening et al, 2016;Clark et al, 2019). There are a variety of deep sea studies using benthic imagery and encompassing a broad range of objectives including biodiversity assessments (Thresher et al, 2014;Auscavitch et al, 2020;Lapointe et al, 2020;Salinas-de-León et al, 2020), identification of vulnerable marine ecosystems (VME) (FAO, 2009;Jones and Lockhart, 2011;Dautova et al, 2019;Baco et al, 2020;Williams et al, 2020a), marine protected area (MPA) planning (Davies et al, 2017) and monitoring and recovery studies related to activities such as fishing (Althaus et al, 2009;Clark et al, 2019;Baco et al, 2020;Williams et al, 2020b) and potential seabed mining (Boschen-Rose et al, 2021).…”

“…The requirements for taxonomic resolution differ depending on the specific objectives of the study. High resolution taxonomic information is required for biodiversity studies reliant on species identifications (Auscavitch et al, 2020;Lapointe et al, 2020;Salinas-de-León et al, 2020). Multivariate analyses of community structure or bioregional studies are not as reliant on species level data, because data are commonly combined over several taxa or aggregated to higher taxonomic levels (Williams et al, 2010;Tanner et al, 2018;Clark et al, 2019).…”

“…This has led to the development of other taxonomic and morphological based classification schemes for the identification and annotation of marine fauna from imagery. Most studies use a set of region-specific phototaxa/morphospecies termed operational taxonomic units (OTUs) that are usually identified based on a combination of taxonomic knowledge and appearance including morphology and/or color; these are considered a proxy for species (Bewley et al, 2015;Howell et al, 2019;Auscavitch et al, 2020;Horton et al, 2021). This approach requires understanding and knowledge of the regional species pool, taxonomic and annotation expertise and is expensive (Williams et al, 2010;Schoening et al, 2016).…”