Using 3D photogrammetry from ROV video to quantify cold-water coral reef structural complexity and investigate its influence on biodiversity and community assemblage

Fine-scale structural complexity created by reef-building coral in shallow-water environments is influential on biodiversity, species assemblage and functional trait expression. Cold-water coral reefs are also hotspots of biodiversity, often attributed to the hard surface and structural complexity p...

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Bibliographic Details
Published in:	Coral reefs Vol. 38; no. 5; pp. 1007 - 1021
Main Authors:	Price, David M., Robert, Katleen, Callaway, Alexander, Lo lacono, Claudio, Hall, Rob A., Huvenne, Veerle A. I.
Format:	Journal Article
Language:	English
Published:	Berlin/Heidelberg Springer Berlin Heidelberg 01-10-2019 Springer Nature B.V
Subjects:	Abundance Biodiversity Biomedical and Life Sciences Canyons Cold Collinearity Communities Community structure Complexity Coral reefs Digital Elevation Models Epifauna Fish Freshwater & Marine Ecology Life Sciences Marine environment Niches Nucleotide sequence Oceanography Photogrammetry Resolution Shallow water Spatial analysis Species richness Three dimensional models Tropical climate Underwater vehicles Unmanned vehicles Water temperature Rugosity Cold-water coral Reef community Structure from motion Habitat threshold Structural complexity
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Summary:	Fine-scale structural complexity created by reef-building coral in shallow-water environments is influential on biodiversity, species assemblage and functional trait expression. Cold-water coral reefs are also hotspots of biodiversity, often attributed to the hard surface and structural complexity provided by the coral. However, that complexity has seldom been quantified on a centimetric scale in cold-water coral reefs, unlike their shallow-water counterparts, and has therefore never been linked in a similar way to the reef inhabitant community. Structure from motion techniques which create high-resolution 3D models of habitats from sequences of photographs is being increasingly utilised, in tandem with 3D spatial analysis to create useful 3D metrics, such as rugosity. Here, we demonstrate the use of ROV video transect data for 3D reconstructions of cold-water coral reefs at depths of nearly 1000 m in the Explorer Canyon, a tributary of Whittard Canyon, NE Atlantic. We constructed 40 3D models of approximately 25-m-length video transects using Agisoft Photoscan software, resulting in sub-centimetre resolution reconstructions. Digital elevation models were utilised to derive rugosity metrics, and orthomosaics were used for coral coverage assessment. We found rugosity values comparable to shallow-water tropical coral reef rugosity. Reef and nearby non-reef communities differed in assemblage composition, which was driven by depth and rugosity. Species richness, epifauna abundance and fish abundance increased with structural complexity, being attributed to an increase in niches, food, shelter and alteration of physical water movement. Biodiversity plateaued at higher rugosity, illustrating the establishment of a specific reef community supported by more than 30% coral cover. The proportion of dead coral to live coral had limited influence on the community structure; instead, within-reef patterns were explained by depth and rugosity, though our results were confounded to a certain extent by multi-collinearity. Fine-scale structural complexity appeared to be integral to local-scale ecological patterns in cold-water coral reef communities.
ISSN:	0722-4028 1432-0975
DOI:	10.1007/s00338-019-01827-3