Quantifying the shelter capacity of coral reefs using photogrammetric 3D modeling: From colonies to reefscapes
2021
Urbina-Barreto, Isabel | Chiroleu, Frédéric | Pinel, Romain | Fréchon, Louis | Mahamadaly, Vincent | Elise, Simon | Kulbicki, Michel | Quod, Jean-Pascal | Dutrieux, Eric | Garnier, Rémi | Bruggemann, J. Henrich | Penin, Lucie | Adjeroud, Mehdi | CREOCEAN OI | Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE [Nouvelle-Calédonie]) ; Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Délégation Ifremer de Nouvelle-Calédonie ; Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Nouvelle-Calédonie (UNC)-Centre National de la Recherche Scientifique (CNRS) | Laboratoire d'Excellence CORAIL (LabEX CORAIL) ; Institut de Recherche pour le Développement (IRD)-Université des Antilles et de la Guyane (UAG)-École des hautes études en sciences sociales (EHESS)-École Pratique des Hautes Études (EPHE) ; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de La Réunion (UR)-Université de la Polynésie Française (UPF)-Université de la Nouvelle-Calédonie (UNC)-Institut d'écologie et environnement-Université des Antilles (UA) | Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Université de La Réunion (UR)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Département Systèmes Biologiques (Cirad-BIOS) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad) | GEOLAB S.A. ; GEOLAB S.A. | Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE [Perpignan]) ; Institut de Recherche pour le Développement (IRD) | Agence pour la Recherche et la Valorisation Marines - ARVAM (Ste Clotilde, La réunion-France) ; Agence pour la Recherche et la Valorisation Marines - ARVAM (Ste Clotilde, La réunion-France) | Centre de recherches insulaires et observatoire de l'environnement (CRIOBE) ; Université de Perpignan Via Domitia (UPVD)-École Pratique des Hautes Études (EPHE) ; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS) | The authors are thankful to Sophie Bureau, Christophe Peignon, Mahe Dumas and Bertrand Bourgeois for their help in data collection, Claude Payri, Corina Iovan, Pascal Dumas and Veronique Perrin (IRD Noumea, New Caledonia) for logistic support and the captain and sailor of the research vessel Archamia, Philippe and Sam, for their help in fieldwork. We further thank the CORCOPA program funded through the European Best 2.0 program for invitation to collaborate, Ocean Inovation Tour and the crew of the sailing vessel Antsiva, Nicolas and Anne Tisne, Odilon and Jonathan, for logistic support, and the Terres Australes et Antarctiques Francaises (TAAF) for research permits for the Europa mission. | ANR-10-LABX-0008,CORAIL,Coral reefs facing global change(2010)
International audience
Show more [+] Less [-]English. Structural complexity plays a key role in the functioning of coral reef ecosystems. Reef-building corals are major contributors to this complexity, providing shelter and food for numerous invertebrates and fish species. Both structural complexity and shelter capacity of reefscapes are determined by several components such as spurs and grooves, slope, caves and holes, vegetation and coral colonies. Quantifying the shelter capacity from coral col-onies to reefscapes is a fundamental step to estimating ecosystem potential to support biodiversity. Here, we applied underwater photogrammetry to quantify shelter volumes provided by individual coral colonies. Overall, 120 3D models of coral colonies from branching, massive, columnar and tabular growth forms were studied. Three reefscapes were also 3D modeled. The study encompasses three Indo-Pacific Islands: Reunion, Europa and New Caledonia. At the colony level, measurements of diameter, planar area, surface and shelter volume were computed. At the reefscape, the diameter and planar area of each colony were extracted from orthomosaics and then used to estimate shelter capacity. Linear models had high accuracy for predicting shelter volume (a 3D metric) from 2D metrics: the diameter=83.1%, R2=0.95; the planar area=87.5%, R2=0.95 and the colony surface=87.3%, R2=0.96. The surface complexity and the shelter volume of the colonies allowed inferring the size of shelters provided by coral growth forms. Quantitative descriptors (i.e. relative percentage of shelter by growth form, the abundance of coral colonies, “Shannon-Shelter Index”) revealed reefscape-scale shelter differences. Our major finding is that planar area and diameter of coral colonies are satisfactory proxies for estimating shelter volume. These new proxies allow 2D metrics to quantify 3D shelter provision, which can support sci-entists and managers in conservation actions since such metrics are widely used in monitoring programs. Future investigations on the relationships between shelter provision and reef biodiversity will improve the under-standing of these complex ecosystems
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