Part of the regional summaries: Chagos Archipelago - Peros Banhos and Chagos Archipelago
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Chagos (NOAA CRW virtual station)A sheltered lagoon patch reef at 29 m where Acropora makes up 87% of the coral, as dense staghorn thickets and table shelves over old dead framework in the shallows, at 56% cover. Several photos show conspicuous white table corals despite a very low published bleaching figure, a mismatch that remains unresolved. Surveyed on the Living Oceans Foundation's Global Reef Expedition.
Four independent survey stations shown with the program’s logo — click one to see how far it is from this site.
Five other CRD dive sites within 5 km shown in orange — click a marker to open its page.
🗺 Detailed map of the Global Reef Expedition dive sites, Peros Banhos, Chagos (Khaled bin Sultan Living Oceans Foundation; opens in a new window)
25 of these 32 photographs are shown beside the text that discusses them under "Site description" below.
Site description
Setting
A protected, submerged lagoonal patch reef in Peros Banhos at 29 m.
General benthic features
The reef is overwhelmingly a single-genus system: Acropora makes up 87% of all coral recorded, forming dense staghorn thickets and tabular shelf structures over standing dead-coral framework in the shallows (e.g., Image 1, Image 3, Image 7, Image 8, Image 10, Image 11, Image 12, Image 13, Image 14, Image 16, Image 17, Image 21, Image 24, Image 32).
Coral cover and Acropora dominance both fall sharply with depth, giving way at the deepest station to a sparse, algae-dominated community of scattered massive corals (e.g., Image 5, Image 9, Image 23, Image 26, Image 30).
Coral cover
Image-based methods read this reef 23–24 points lower than the transects (CoralNet 31.7%, Coralscapes 32.8%); the three are not interchangeable and should not be averaged (see the full report).
Stressors
Despite the very low published bleaching figure, several photographs show conspicuous, colony-scale white pallor among the tabular corals, a discrepancy that remains unresolved (e.g., Image 4, Image 15, Image 20, Image 22, Image 29, Image 33).
The bleaching percentage is a computer vision figure — CoralNet annotation of the informal survey images, not a diver's field estimate — and human-vs-model agreement is weaker for bleaching (r = 0.40) than for coral cover (r = 0.72). No crown-of-thorns starfish (COTS) or other corallivores evident.
Comparisons with other data
A published figure above about 70% usually reflects the surveyors choosing the most coral-rich patch, so read it as a best-patch number rather than a site mean.
CV model comparison
More info
Those are point counts on the photographs; this is a diver swimming a transect. The models and the reference never saw the same thing. ⚠ SITE-LEVEL ONLY. The 2,500 frames were not associated with any transect taken within 200 m of them, so transect-vs-image comparisons are site means, never frames. The transect value is already in the pin `cover` field (109 of 112 pins, sourced to the paper's suppl. S1) and is read from there, never re-imported. The transect is THE coral-cover value for this site and stands alone. The rows below it are a methods comparison only: no computer-vision value is averaged with it, feeds the headline, or carries over to the site's cover figure (Anderson, 2026-09-22).| Method | Hard-coral cover (%) |
|---|---|
| Transect (published) | 56.0 |
| In-house DINOv3 | 33.3 |
| CoralSCOP edited | 38.4 |
| Claude | 35.0 |
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| Sheppard et al. (2008) | 2006 | 1 station, 2.82 km | Records ↓ |
| Spalding et al. (2024) | 2024 | 2 stations, 1.91 km | Records ↓ |
| Spalding et al. 2025 (Chagos 2024 bleaching report) | 2024 | 2 stations, 1.91 km | Records ↓ |
| XL Catlin Seaview Survey | 2015 | 1 station, 4.62 km | Records ↓ |
Dr. Coral (CRD)Year-average (no detectable trend)Within 5 km, 6 independent survey stations recorded hard coral cover in 10 records between 2006 and 2024. Surveys since 2021 average 70% (range 70%, n=2); 2 best-patch values above 70% are left out, as they are not site means. This site's own estimate (56%) sits 14.0 points below the recent range (70%); the methods differ, so the comparison is context, not a like-for-like test.
Collected by other programs using different methods (the XL Catlin Seaview Survey uses photo-transects with automated image annotation), so these are context for the figures above, not a like-for-like comparison. Where a station was surveyed more than once the range is shown. Station names are not dive-site names. Values marked best patch exceed 70%: surveyors usually chose the richest area, so they are not site means.
| Agency | Site / location | Date | Hard coral cover (%) | Distance | Link |
|---|---|---|---|---|---|
| Sheppard et al. (2008) | Peros Banhos | 2006 | 44% (5 surveys) | 2.82 km | HeatCRD database |
| XL Catlin Seaview Survey | transect 36006 | 2015 | 27% | 4.62 km | — |
| Spalding et al. 2025 (Chagos 2024 bleaching report) | Peros Banhos - lagoon Knoll (N, 9-12 m) | 2024 | 80% best patch | 1.91 km | — |
| Spalding et al. 2025 (Chagos 2024 bleaching report) | Peros Banhos - lagoon Knoll (N, 6-9 m) | 2024 | 70% | 1.91 km | — |
| Spalding et al. (2024) | Peros Banhos - lagoon Knoll (N, 9-12 m) | 2024 | 80% best patch | 1.91 km | — |
| Spalding et al. (2024) | Peros Banhos - lagoon Knoll (N, 6-9 m) | 2024 | 70% | 1.91 km | — |
Data & links
- Read the full site report ↗
- Download benthic survey data (CSV) ↗
- Download all LOF-GRE data (933 sites) ↗
- CoralNet image repository for this region ↗
- HeatCRD database ↗
- (reference) ↗
- Photo portfolio ↗
- Coral Reef Diagnostics page for this area ↗
All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics and the organizations named in the data-sources table above.
© Coral Reef Diagnostics.
References
- Mayfield AB, Dempsey AC (2026). Using tourist diver images to estimate coral cover and bleaching prevalence in a remote Indian Ocean coral reef system. Oceans 7(1):1. PDF
- Sheppard C, Harris A, Sheppard A (2008). Archipelago-wide coral recovery patterns since 1998 in the Chagos Archipelago, central Indian Ocean. Marine Ecology Progress Series 362:109-117. PDF
- Spalding M, Bourasseau M, et al. (2025). Coral bleaching and mortality in the Chagos Archipelago, 2024. British Indian Ocean Territory Administration report (gray literature). PDF