Journal Article

Predicting the Distribution of Mesophotic Coral Ecosystems in the Chagos Archipelago

Robinson, Edward, Hosegood, Phil, Diaz, Clara, Foster, Nicola L., Graves, Kyran P., Bolton, Adam, Howell, Kerry L.

2025

Overview

To support conservation efforts, accurate mapping of marine organism community’ distribution has become more critical than ever before. While previous mapping endeavours have primarily focused on easily accessible shallow‐water habitats, there remains limited knowledge about the ecosystems lying beyond SCUBA diving depths, such as mesophotic coral ecosystems (MCEs, ~30–150 m). MCEs are important habitats from an ecological and conservation perspective, yet little is known about the environmental factors that shape these ecosystems and their distribution, particularly in the Indian Ocean region. The goals of this study are to (1) predict the spatial distribution and extent of distinct benthic communities and MCEs in the Chagos Archipelago, central Indian Ocean, (2) test the effectiveness of a range of environmental and topography derived variables to predict the location of MCEs around Egmont Atoll and the Archipelago, and (3) independently validate the models produced. In addition, we compared the MCEs predicted extent in the Archipelago for the models derived from high‐resolution multibeam and low‐resolution GEBCO bathymetry data. Using maximum entropy modelling, all models resulted in excellent (> 0.9) performances, for AUC and threshold‐dependent metrics, predicting extensive and previously undocumented MCEs across the entire Archipelago with, however, differences in the predicted extent between the high‐ and low‐resolution models. Independent validation resulted in fair (> 0.7 AUC) and poor (> 0.6 AUC) performances for the high‐resolution and low‐resolution models, respectively. Photosynthetically active radiation (PAR), temperature, chlorophyll‐a, and topographically derived variables were identified as the most influential predictors. In conclusion, this study provides the first prediction of the distribution of MCEs and their distinct benthic communities in the Archipelago. It highlights their significance in terms of potential extent and response to various environmental factors, supporting decision making for prioritising future survey sites to study MCEs across the Archipelago and targeting ecologically important areas for conservation. This study aims to map and predict the distribution of mesophotic coral ecosystems (MCEs) in the Chagos Archipelago, Indian Ocean, using high‐ and low‐resolution bathymetry data. The models, developed using environmental and topographical variables, showed excellent predictive performance, revealing extensive, previously undocumented MCEs; though independent validation showed stronger results for high‐resolution data. The findings offer valuable insights for conservation efforts by highlighting the ecological importance of MCEs and guiding future research and conservation priorities in the region.

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc,Wiley
• Subject: Archipelagoes / Atolls / Bathymetry / Benthic communities / Biodiversity / Biodiversity Ecology / Biogeography / Central Indian Ocean / Climate change / Community Ecology / Conservation / Conservation areas / Data collection / Decision making / ecology / Ecosystem Ecology / Ecosystems / Environmental factors / Habitats / independent validation / Mapping / Marine ecosystems / Maximum entropy / maximum entropy modelling / mesophotic / Ocean bottom / Organisms / Photosynthetically active radiation / Scuba diving / Spatial distribution / Spatial Ecology / species distribution modelling / Taxonomy