Part of the regional summaries: Chagos Archipelago - Salomon / Blenheim / Speakers Bank and Chagos Archipelago
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Chagos Archipelago, UK (NOAA CRW virtual station)A high-cover Salomon forereef (71% coral) led by Acropora but with a large share of plate-forming Montipora and Pachyseris, very little algae, and no sediment. Note that every figure rests on a single 100-point transect, so the numbers are less certain. Surveyed on the Living Oceans Foundation's Global Reef Expedition.
CTD-cast midpoint of 29.9–31.6°C
Eight independent survey stations shown with the program’s logo — click one to see how far it is from this site.
Six other CRD dive sites with their own pages within 5 km shown in orange — click a marker to open its page.
🗺 Detailed map of the Global Reef Expedition dive sites, Salomon Atoll, Chagos (Khaled bin Sultan Living Oceans Foundation; opens in a new window)
Site description
General benthic features
The transect records nine genera, and the reef is Acropora-led but not Acropora-only: Acropora 38% of the benthos (54% of live coral), Montipora 12% (17%), Pachyseris 7.0% (9.9%), Favia 4.0%, Porites 3.0%, then Goniastrea, Lobophyllia, and Montastrea at 2.0% each, and Astreopora 1.0%. H′ = 1.52, Simpson = 0.67, J′ = 0.69. The Montipora figure is the distinctive one — 12% of the benthos and 17% of live coral is a large plating/encrusting component, and with Pachyseris at 7.0% more than a quarter of this reef's coral is plate-forming rather than branching or massive. Richness is 9, but one 100-point transect cannot record most of the genera present (see Other notes), so that number is not trustworthy. Total algae is 20%, split evenly between CCA 7.0% and erect algae 7.0% (35% each), with plain turf 5.0% and macroalgae 1.0%. Sediment-laden turf and cyanobacteria both read exactly zero. Bare substrate 9.0%, pavement 21%, and sand, rubble, and non-coral invertebrates (PITS) all read zero. A high-cover, low-algae, CCA-and-erect-algae forereef with essentially no sediment signal.
Coral cover
- Reference: Mayfield & Dempsey (2026)
- CoralNet submission package
- The 71% headline is 71 points out of 100 on one transect; the published station value is the same 71% (Mayfield & Dempsey 2026, Oceans, supplemental S1).
- Coral cover: 71%.
- Live hard coral measured on the in situ benthic transects of the LOF BIOT-1 expedition (Mayfield & Dempsey 2026, Oceans, supplemental S1), against total algal cover (all algal groups) of 20% of the benthos.
- The transect figure is this site's authoritative cover value; no image-derived product overrides it.
Stressors
Dead coral is 8.0%, recently dead 0%. The Living Oceans Foundation transects here recorded no cyanobacteria.
Comparisons with other data
The XL Catlin Seaview Survey covered a nearby station (transect 36018) in 2015, 1.25 km from the pin; we could not confirm that it is the same reef. Within 5 km, eight independent stations recorded station-year means of 6.8–63% hard coral cover between 2006 and 2020; the nearest, XL Catlin Seaview Survey at transect 36018, 1.25 km away, read 22% in 2015.
Other notes
Replication — the site's central weakness, and it is severe. BISA98 rests on one transect, one depth stratum (D4), 100 points. Every figure above is one 100-point read — hence the whole integers — and no standard deviation, depth profile, range, or confidence interval can be given for any of them.
No underwater photographs from this station are on file.
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| Lange et al. (2021) | 2006–2020 | 1 station, 0.48 km | Records ↓ |
| Sheppard et al. (2008) | 2006 | 1 station, 3.69 km | Records ↓ |
| Spalding et al. (2025) | — | 1 station, 3.81 km | Records ↓ |
| XL Catlin Seaview Survey | 2015 | 6 stations, 1.25–4.92 km | Records ↓ |
LOF Global Reef ExpeditionYear-average (illustrative only, programs differ)Within 5 km, 8 independent survey stations recorded hard coral cover in 16 records between 2006 and 2020. The one station surveyed in more than one year declined by 27 points between its first and latest surveys. The longest record, Salomon Atoll (Lange et al. 2021, 0.48 km away), went from 48% in 2006 to 21% in 2020. The most recent nearby survey is from 2020, so these values predate recent heat stress. This site's own estimate (71%) sits 8 points above the range of these station-year means up to 2 km away (6.8–63%); the methods differ, so the comparison is context, not a like-for-like test. One further row in the table has no survey date, so it is listed but not part of this summary.
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 cell shows either the range of its values or, as a single value, the mean of surveys made in one year. Station names are not dive-site names.
| Agency | Site / location | Date | Hard coral cover (%) | Distance | Link |
|---|---|---|---|---|---|
| Lange et al. (2021) | Salomon Atoll | 2006–2020 | 6.8–63% (range of yearly means; 5 records) | 0.48 km (atoll-level position) | doi:10.1007/s00338-021-02184-w |
| Sheppard et al. (2008) | Salomon | 2006 | 32% (5 records) | 3.69 km | doi:10.3354/meps07436 |
| XL Catlin Seaview Survey | transect 36018 | 2015 | 22% | 1.25 km | doi:10.14264/uql.2019.930 |
| XL Catlin Seaview Survey | transect 36013 | 2015 | 28% | 1.35 km | doi:10.14264/uql.2019.930 |
| XL Catlin Seaview Survey | transect 36015 | 2015 | 28% | 3.57 km | doi:10.14264/uql.2019.930 |
| XL Catlin Seaview Survey | transect 36014 | 2015 | 34% | 4.05 km | doi:10.14264/uql.2019.930 |
| XL Catlin Seaview Survey | transect 36016 | 2015 | 19% | 4.61 km | doi:10.14264/uql.2019.930 |
| XL Catlin Seaview Survey | transect 36017 | 2015 | 22% | 4.92 km | doi:10.14264/uql.2019.930 |
| Spalding et al. (2025) | Salomon - Boddam Lagoon (N, 1-4 m) | pre-bleaching baseline | 65% | 3.81 km | — |
Data & links
- Download benthic survey data (CSV) ↗
- Download all LOF-GRE data (933 sites) ↗
- CoralNet image repository for this region ↗
- Photo portfolio ↗
- Coral Reef Diagnostics page for this area ↗
Data are from the Khaled bin Sultan Living Oceans Foundation Global Reef Expedition, Coral Reef Diagnostics, and the organizations named in the data sources above.
© Coral Reef Diagnostics.
References
- Lange ID, Benkwitt CE, McDevitt-Irwin JM, Tietjen KL, Taylor B, Chinkin M, et al. (2021). Wave exposure shapes reef community composition and recovery trajectories at a remote coral atoll. Coral Reefs 40:1819-1829. 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
- 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
- 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
- Gonzalez-Rivero M, et al. (2019). Seaview Survey photo-quadrat and image classification dataset. The University of Queensland (UQ eSpace) data collection. DOI