Part of the regional summaries: Chagos Archipelago - Peros Banhos and Chagos Archipelago
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Chagos (NOAA CRW virtual station)A low sand-and-rubble channel reef at 23 m with just 7% coral cover, one of the lowest in Chagos, made up almost entirely of scattered Porites. Dense stands of gorgonian sea fans and abundant sea urchins fill the gaps, and a reef manta ray cruised over the site. Surveyed on the Living Oceans Foundation's Global Reef Expedition.
Three independent survey stations shown with the program’s logo — click one to see how far it is from this site.
Two 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)
4 of these 13 photographs are shown beside the text that discusses them under "Site description" below.
Site description
Setting
BIPB66 is an intermediate-exposure, emergent channel reef on the Peros Banhos forereef, surveyed at 23 m.
General benthic features
The coral present is almost a single-genus assemblage, with Porites accounting for roughly two-thirds of all coral cover and only nine other genera recorded in trace amounts. Underwater photographs show a low-relief sand-and-rubble plain with scattered massive coral colonies (e.g., Image 1), dense gorgonian sea fan stands, and abundant sea urchins, plus one small coral colony showing clear localized partial bleaching.
Coral cover
Coral cover is only 7.0%, one of the lowest values recorded anywhere in the Chagos survey, against a much higher 52.1% algal cover (mostly crustose coralline algae and turf rather than fleshy macroalgae); published image bleaching is 6.3%. 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). Image-based methods read this reef higher than the transects here — CoralNet 9.4%, Coralscapes 23.1% against a transect figure of 7.0%, the reverse of the pattern at most Chagos sites; the three are not interchangeable and should not be averaged (see the full report).
Stressors
No crown-of-thorns starfish (COTS) or other corallivores evident.
Fish and other fauna
A reef manta ray was also photographed cruising over the site (e.g., Image 2, Image 3, Image 4).
Comparisons with other data
No independent survey was made at this exact site; the nearest ones are listed in the table below.
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) | 7.0 |
| In-house DINOv3 | 26.1 |
| CoralSCOP edited | 28.8 |
| Claude | 2.3 |
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| Sheppard et al. (2008) | 2006 | 1 station, 4.31 km | Records ↓ |
| Spalding et al. 2025 (Chagos 2024 bleaching report) | 2024 | 2 stations, 3.17 km | Records ↓ |
Dr. Coral (CRD)Year-average (no detectable trend)Within 5 km, 3 independent survey stations recorded hard coral cover in 7 surveys between 2006 and 2024. One survey since 2021 recorded 70%; 1 best-patch value above 70% is left out, as they are not site means. This site's own estimate (7.0%) sits 63.0 points below the recent value (70%); the methods differ, so the comparison is context, not a like-for-like test.
Collected by other programs using different methods, 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) | 4.31 km | HeatCRD database |
| Spalding et al. 2025 (Chagos 2024 bleaching report) | Peros Banhos - lagoon Knoll (N, 9-12 m) | 2024 | 80% best patch | 3.17 km | — |
| Spalding et al. 2025 (Chagos 2024 bleaching report) | Peros Banhos - lagoon Knoll (N, 6-9 m) | 2024 | 70% | 3.17 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