Chagos Archipelago - Great Chagos Bank West / Brothers / Eagle
Regional summary of 50 dive sites. Figures are averages across the sites that report them (n = sites with a value); each site's own page has its individual values. Part of the Chagos Archipelago overview.
⬇ Download this region as a report card
The western Great Chagos Bank's 50 reefs, mostly sheltered lagoon, bank, and channel sites dived in March 2015, range from algae-dominated banks to the high-cover Three Brothers reefs, where one depth band was 93% blue coral. Sharks were seen throughout, and young corals were recolonizing old dead pavement.
Heat stress
Long-term record: 3 years from 1985 through 2025 reached 8 or more °C-weeks at NOAA’s Chagos Archipelago, UK station. Download the annual DHW data (CSV).
50 sites in this region — click a marker to open that site.
Regional setting
This unit sits on the western side of the Great Chagos Bank, a mostly submerged atoll that Spalding et al. (2001) rank as the world's largest atoll structure, at about 13,000 km². The atlas map places Eagle, the Three Brothers, and Danger Island along the western rim, and both Danger Island and the Three Brothers and Resurgent Islands were declared Strict Nature Reserves in 1998. Spalding et al. (2001) treat the Central Indian Ocean as a zone of transition, with coral diversity peaking in a narrow band, the "Chagos Stricture", centered on the southern Maldives and the Chagos. The Chagos reefs alone hold some 220 scleractinian species, with faunal ties to both Indonesia and East Africa. The same chapter ranks the Chagos among the least impacted reefs anywhere, and cites water-quality studies suggesting its waters are among the least polluted on Earth. Low human pressure did not spare these reefs from the 1998 bleaching, however. Corals had typically covered 50–80% of seaward and lagoon slopes to about 40 m, and seaward reefs are estimated to have lost 80–85% of their coral, on average. Spalding et al. (2001) estimate about 3,770 km² of reef across the whole archipelago, and Souter et al. (2021) give 2,731 km² for the Chagos ecoregion.
Wilkinson (2006), drawing on the 2004 status report, describes encouraging recovery in the Chagos after the 1998 die-off. Souter et al. (2021) show Chagos coral cover rising until about 2015 before the 2016 bleaching reversed the gains. That event killed more than 42% of living hard coral across South Asia, yet mortality was lower than in 1998, partly because less coral was left to die and partly because the surviving communities held more bleaching-resistant species. In 1998, Acropora and Echinopora had been the most vulnerable genera. Localized bleaching continued from 2017 to 2019. Souter et al. (2021) describe the Chagos atolls as protected, lightly pressured reefs, within the region's largest marine protected area (MPA), for which bleaching is the main threat.
Overview
This unit covers 50 sites on the western Great Chagos Bank, surveyed between 12 and 28 March 2015: the Three Brothers group, Eagle Island, the Danger Island reefs, and a set of Central Chagos lagoon banks. The majority are sheltered lagoon, bank, and channel reefs, with fringing reefs and forereefs off North, Middle, and South Brother. Logged maximum depths ran from 8.2 m at BIEA24.5 to 31.1 m at BIEA24 (BITB49 has a station CTD cast only).
Coral cover ranged from 4.2% on the seagrass meadow at BIDI12 and 6.3% at BIEA17, smothered by sediment-laden turf, to 62% at BITB34 and 67% at BITB58. BITB58 has one depth band that is 93% blue coral (Heliopora) and the next 80% Acropora, and BITB34 is built around whorled plate-coral mounds two to three meters across. BITB39 and BITB54 each carry 34 coral genera, including the endemic Ctenella at BITB39. Eagle Island and the Central Chagos banks are sparse, Porites-heavy, and rubble-strewn, and BICC51 has 70% algal cover. At Danger Island, BIDI08 reached 61% cover on large tabular plates, while BIDI12 and BIDI13 are dominated by seagrass meadows (Anderson's field notes).
These were early-season dives; Anderson's sampling sheet logs scattered bleached colonies from mid-March, more through late April, and bleaching was most widespread in early May. At the formal survey stations, published values ranged from 0% at four sites to 24% at BICC50; the two informal '.5' stations, reported separately, recorded 28% (BIEA24.5) and 17% (BITB34.5). Colony-scale partial bleaching was nonetheless photographed at BIEA19, BIDI14, BITB39, BITB43, BITB44, BITB53, and BITB58, and small bone-white colonies appear at BIDI16 and BIEA52, where Anderson's sampling sheet logs one sampled colony at each as 10% bleached (published values 0%). A crown-of-thorns starfish was photographed beside forceps at BIEA52 (one individual, no aggregation), and another beside a gloved hand holding forceps at BITB55, the only one Anderson's sampling sheet notes at that site. A clean white lesion of unresolved cause was photographed on one brain coral at BIDI10. At BITB44, dense young Acropora recruits on old dead pavement show the reef recolonizing.
Sharks were seen throughout. Sharks compatible with gray reef sharks cruised the seagrass meadow at BIDI12 in twelve frames, whitetip reef sharks were recorded at many sites, and a nurse-type shark appeared at BIEA26. Other sightings included three spotted eagle rays together at BITB34, giant clams at several sites, a sea turtle at BICC35, and a school of several hundred trevally at BITB33.
Highlights
- BITB58: 67% cover, with one depth band 93% blue coral (Heliopora)
- BITB39 and BITB54 each carry 34 coral genera
- BICC51 has 70% algal cover
- Crown-of-thorns: single starfish photographed beside forceps at BIEA52 and BITB55
- BIDI08: 61% cover on large tabular plates; logged depths across the unit ran from 8.2 m (BIEA24.5) to 31.1 m (BIEA24)
- Three spotted eagle rays photographed together at BITB34
Notable observations (19)
- Chagos Archipelago - Great Chagos Bank West (BIEA52): Crown-of-thorns starfish photographed beside stainless-steel bone-cutting forceps; one individual, no aggregation. Published bleaching 0%, yet one frame shows a small intact bone-white colony, and one of the two colonies Anderson sampled here was 10% bleached.
- Chagos Archipelago - Great Chagos Bank West (BITB55): One crown-of-thorns starfish photographed beside a gloved hand holding forceps, the only one Anderson's sampling sheet notes at the site. Published bleaching 8.1%; one sampled colony logged as 35% sickly or diseased.
- Chagos Archipelago - Great Chagos Bank West (BIDI10): Disease/lesion: a clean white lesion across a brain coral, which could be disease, predation scarring, or physical damage (unresolved); a pale tiered plating colony read as older mortality.
- Chagos Archipelago - Great Chagos Bank West (BIDI13): A distinct dark brown dead patch of unclear age between two large massive colonies, with a small branching recruit settled nearby.
- Chagos Archipelago - Great Chagos Bank West (BIDI14): Bleaching 9.8%: cream-white branch tips on Acropora and a small Pocillopora-type colony partly bleached cream-white; a meandroid brain coral with old partial mortality on its upper third, crusted by coralline and turf algae.
- Chagos Archipelago - Great Chagos Bank West (BIEA19): Bleaching: a thick-branched Pocillopora-type colony strongly mottled with bone-white patches (published 2.6%); dead and dying tabular Acropora nearby; one of six sampled colonies 60% bleached or recently dead.
- Chagos Archipelago - Great Chagos Bank West (BITB44): Two colonies with textbook partial bleaching (published 5.98%). No crown-of-thorns, disease lesion, or predation visible in the photographs, though Anderson's sheet logs two sampled colonies as bleached/diseased.
- Chagos Archipelago - Great Chagos Bank West (BITB43): What the data say: published bleaching 0%. What Anderson saw: three partly bleached branching colonies, each with a sharply bounded group of stark-white branches; the sampling sheet logs one sampled colony as 50% diseased or dead and another as sickly. No crown-of-thorns or disease visible in the photographs.
- Chagos Archipelago - Great Chagos Bank West (BIDI16): Logged at 0.0% bleached, but one small bright bone-white branching colony is visible, and one of the two colonies Anderson sampled here was 10% bleached.
- Chagos Archipelago - Great Chagos Bank West (BITB42): Two colonies with clean bone-white skeleton; severe bleaching cannot be separated from very recent tissue loss (published 7.73%); one sampled colony logged as 80% dead or bleached. No crown-of-thorns or disease visible in the photographs.
- Chagos Archipelago - Great Chagos Bank West (BITB41): Paling real but patchy: a stark-white branching colony with green algae only at its base, and white branch tips on an otherwise pigmented branching colony (published 7.65%); one of four sampled colonies 10% bleached or pale. No crown-of-thorns.
- Chagos Archipelago - Great Chagos Bank West (BIEA20): One branching colony chalky gray-white with early algal film, either bleached tissue or a recently dead colony (a photograph cannot separate the two).
- Chagos Archipelago - Great Chagos Bank West (BIEA18): Patches of mostly old, crusted partial mortality on a brown massive Porites; published bleaching 12%.
- Chagos Archipelago - Great Chagos Bank West (BIEA24): Pale gray patches and small pink spots on a large massive dome at the site, with no sharp-edged patch of freshly exposed skeleton (cause not diagnosable from an image); published bleaching 21%, and the two colonies Anderson sampled here were 20% and 50% bleached.
- Chagos Archipelago - Eagle Island (BIEA24.5): Bubblegum-pink and magenta Pocillopora (natural color or a stress response; the photographs cannot tell which); localized but severe coral death, including a branching colony in mid-collapse. Published bleaching 28% (from 5 photographs).
- Chagos Archipelago - Great Chagos Bank West (BICC50): Published bleaching 24%; Anderson's sampling sheet independently logs one colony sampled here as 40% bleached (ChJo136). No disease or crown-of-thorns.
- Chagos Archipelago - Great Chagos Bank West (BITB56): Published bleaching 16%; no bleached colony is visible in the 13 frames, and the three colonies Anderson sampled here were 5-10% pale, bleached, or sickly.
- Chagos Archipelago - Three Brothers lagoon (BITB34.5): Published bleaching 17% (CoralNet, 3 photographs); one wholly white branching colony is either bleached or recently dead, and Anderson's field sheet records all nine colonies sampled on the dive as unbleached, one of them more than 30% dead.
- Chagos Archipelago - Great Chagos Bank West (BITB46): One very large table with sharply bounded partial mortality across 40% of its plate, already colonized by coralline algae (older lesion). No crown-of-thorns, disease, or predation appears in the photographs, although Anderson's field sheet notes one sampled colony with a purple lesion and another as “possibly diseased.”
Sites in this region (50)
- Chagos Archipelago - Eagle Island (BIEA24.5)
- Chagos Archipelago - Great Chagos Bank West (BICC35) — 14% coral cover
- Chagos Archipelago - Great Chagos Bank West (BICC36) — 8.6% coral cover
- Chagos Archipelago - Great Chagos Bank West (BICC50) — 15% coral cover
- Chagos Archipelago - Great Chagos Bank West (BICC51) — 17% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI08) — 61% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI09) — 38% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI10) — 23% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI12) — 4.2% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI13) — 7.2% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI14) — 17% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI15) — 20% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIDI16) — 27% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA17) — 6.3% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA18) — 21% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA19) — 28% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA20) — 13% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA22) — 27% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA23) — 26% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA24) — 16% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA25) — 18% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA26) — 24% coral cover
- Chagos Archipelago - Great Chagos Bank West (BIEA52) — 37% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB27) — 36% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB28) — 31% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB29) — 30% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB30) — 43% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB32) — 30% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB33) — 21% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB34) — 62% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB37) — 40% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB38) — 58% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB39) — 52% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB40) — 45% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB41) — 43% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB42) — 40% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB43) — 30% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB44) — 39% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB45) — 45% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB46) — 32% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB47) — 53% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB48) — 34% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB49) — 26% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB53) — 33% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB54) — 56% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB55) — 51% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB56) — 25% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB57) — 43% coral cover
- Chagos Archipelago - Great Chagos Bank West (BITB58) — 67% coral cover
- Chagos Archipelago - Three Brothers lagoon (BITB34.5)
% coral cover by method
Pooled across 45 dive sites
| Method | Mean % coral cover | Std. dev. between dive sites | n dive sites | Note |
|---|---|---|---|---|
| CoralNet automated point classifier | 31% | ±8.9 | 40 | 22 of these 40 values rest on 10–19 photographs (*) |
| CoralSCOP (SAM-based mask-sum), edited photos | 32% | ±7.7 | 40 | 22 of these 40 values rest on 10–19 photographs (*) |
| Claude (Anthropic), blind point count | 23% | ±9.5 | 40 | 22 of these 40 values rest on 10–19 photographs (*) |
| In-house DINOv3 point classifier | 24% | ±8.5 | 40 | 22 of these 40 values rest on 10–19 photographs (*) |
| In-water diver transect (line/point intercept) | 33% | ±16 | 45 | — |
The mean is an UNWEIGHTED mean of the dive site values — each dive site counts once, whatever its photo count — which is the convention of the published tables and of every other figure on this page. Each value is the one printed on that dive site's own page; a page that prints no value for a method (fewer than 10 photographs) is left out of that method's mean.
This table pools only the 45 dive sites in this unit that have a method comparison; the table for all 101 dive sites is on the Chagos Archipelago page.
Closest to the reference
Over the dive sites where an independent reference exists, CoralNet automated point classifier sits closest to it — a mean absolute deviation of 8.4 pp across 40 dive sites, then Claude (Anthropic), blind point count 10.9 pp (n=40). Not in this ranking: Coralscapes v1, Coralscapes v2, and CoralSCOP (edited), which measure coral area rather than points; DINOv3, which counts points over a different denominator. A mean absolute deviation is not an accuracy score: a model with a consistent offset is correctable, while one with the same deviation scattered in both directions is not.
By dive site
| Dive site | CoralNet | CoralSCOP (edited) | Claude | DINOv3 | Diver transect | Coralscapes v1 | Coralscapes v2 |
|---|---|---|---|---|---|---|---|
| BICC35 | 17%* n=15 | 20%* n=15 | 6.7%* n=15 | 13%* n=15 | 14% | 21%* n=15 | 24%* n=15 |
| BICC36 | 19%* n=15 | 25%* n=15 | 6.4%* n=15 | 18%* n=15 | 8.6% | 21%* n=15 | 27%* n=15 |
| BICC50 | 29%* n=11 | 29%* n=11 | 16%* n=11 | 30%* n=11 | 15% | 37%* n=11 | 48%* n=11 |
| BICC51 | 22%* n=17 | 28%* n=17 | 21%* n=17 | 24%* n=17 | 17% | 27%* n=17 | 28%* n=17 |
| BIDI08 | 36% n=35 | 39% n=35 | 35% n=35 | 29% n=35 | 61% | 50% n=35 | 53% n=35 |
| BIDI09 | 38% n=30 | 32% n=30 | 34% n=30 | 24% n=30 | 38% | 56% n=30 | 61% n=30 |
| BIDI10 | 27%* n=13 | 33%* n=13 | 23%* n=13 | 16%* n=13 | 23% | 44%* n=13 | 49%* n=13 |
| BIDI12 | 10%* n=14 | 18%* n=14 | 2.9%* n=14 | 11%* n=14 | 4.2% | 8.2%* n=14 | 10%* n=14 |
| BIDI13 | 20%* n=11 | 25%* n=11 | 18%* n=11 | 18%* n=11 | 7.2% | 22%* n=11 | 24%* n=11 |
| BIDI14 | too few photos n=9 | too few photos n=9 | too few photos n=9 | too few photos n=9 | 17% | too few photos n=9 | too few photos n=9 |
| BIDI15 | too few photos n=9 | too few photos n=9 | too few photos n=9 | too few photos n=9 | 20% | too few photos n=9 | too few photos n=9 |
| BIDI16 | 26%* n=13 | 31%* n=13 | 24%* n=13 | 22%* n=13 | 27% | 32%* n=13 | 36%* n=13 |
| BIEA18 | 22% n=35 | 28% n=35 | 18% n=35 | 15% n=35 | 21% | 33% n=35 | 32% n=34 |
| BIEA19 | 27%* n=14 | 39%* n=14 | 31%* n=14 | 25%* n=14 | 28% | 42%* n=14 | 45%* n=14 |
| BIEA20 | 25%* n=19 | 27%* n=19 | 22%* n=19 | 16%* n=19 | 13% | 31%* n=19 | 35%* n=19 |
| BIEA22 | 49% n=23 | 50% n=23 | 31% n=23 | 45% n=23 | 27% | 44% n=23 | 46% n=23 |
| BIEA23 | 36% n=24 | 40% n=24 | 29% n=24 | 29% n=24 | 26% | 44% n=24 | 49% n=24 |
| BIEA24 | 41%* n=11 | 39%* n=11 | 37%* n=11 | 41%* n=11 | 16% | 49%* n=11 | 49%* n=11 |
| BIEA25 | 29%* n=19 | 30%* n=19 | 16%* n=19 | 26%* n=19 | 18% | 31%* n=19 | 33%* n=19 |
| BIEA26 | 21% n=30 | 27% n=30 | 15% n=30 | 14% n=30 | 24% | 23% n=30 | 28% n=30 |
| BIEA52 | 38% n=22 | 39% n=22 | 35% n=22 | 22% n=22 | 37% | 50% n=22 | 50% n=22 |
| BITB27 | 34%* n=16 | 38%* n=16 | 24%* n=16 | 24%* n=16 | 36% | 46%* n=16 | 48%* n=16 |
| BITB28 | 27% n=43 | 29% n=43 | 18% n=43 | 20% n=43 | 31% | 34% n=43 | 37% n=43 |
| BITB29 | 30% n=49 | 26% n=49 | 19% n=49 | 24% n=49 | 30% | 40% n=49 | 42% n=49 |
| BITB30 | 30%* n=12 | 30%* n=12 | 14%* n=12 | 18%* n=12 | 43% | 34%* n=12 | 38%* n=12 |
| BITB32 | 17%* n=19 | 20%* n=19 | 12%* n=19 | 12%* n=19 | 30% | 18%* n=19 | 20%* n=19 |
| BITB33 | 20% n=27 | 22% n=27 | 7.9% n=27 | 11% n=27 | 21% | 18% n=26 | 18% n=26 |
| BITB34 | 41%* n=11 | 47%* n=11 | 37%* n=11 | 35%* n=11 | 62% | 56%* n=11 | 67%* n=10 |
| BITB37 | 37% n=56 | 42% n=57 | 29% n=56 | 30% n=57 | 40% | 51% n=55 | 54% n=55 |
| BITB38 | 34% n=44 | 31% n=44 | 26% n=44 | 28% n=44 | 58% | 54% n=44 | 56% n=44 |
| BITB39 | 40% n=60 | 44% n=61 | 37% n=60 | 32% n=61 | 52% | 53% n=59 | 57% n=59 |
| BITB40 | too few photos n=5 | too few photos n=5 | too few photos n=5 | too few photos n=5 | 45% | too few photos n=5 | too few photos n=5 |
| BITB41 | 32%* n=13 | 40%* n=13 | 25%* n=13 | 32%* n=13 | 43% | 40%* n=13 | 42%* n=13 |
| BITB42 | 31% n=49 | 35% n=51 | 23% n=49 | 24% n=51 | 40% | 40% n=50 | 43% n=51 |
| BITB43 | 36%* n=12 | 37%* n=12 | 22%* n=12 | 15%* n=12 | 30% | 47%* n=12 | 50%* n=12 |
| BITB44 | 33% n=36 | 39% n=36 | 27% n=36 | 29% n=36 | 39% | 44% n=36 | 47% n=36 |
| BITB45 | 45%* n=13 | 36%* n=13 | 33%* n=13 | 39%* n=13 | 45% | 51%* n=13 | 52%* n=13 |
| BITB46 | 28%* n=11 | 31%* n=11 | 18%* n=11 | 15%* n=11 | 32% | 35%* n=10 | 38%* n=10 |
| BITB47 | too few photos n=2 | too few photos n=2 | too few photos n=2 | too few photos n=2 | 53% | too few photos n=2 | too few photos n=2 |
| BITB53 | 35% n=22 | 27% n=22 | 23% n=22 | 31% n=22 | 33% | 41% n=22 | 42% n=22 |
| BITB54 | 34% n=99 | 31% n=99 | 30% n=99 | 21% n=99 | 56% | 50% n=97 | 54% n=97 |
| BITB55 | 43%* n=14 | 38%* n=14 | 33%* n=14 | 34%* n=14 | 51% | 47%* n=14 | 51%* n=14 |
| BITB56 | 20%* n=13 | 18%* n=13 | 19%* n=13 | 20%* n=13 | 25% | 25%* n=13 | 26%* n=13 |
| BITB57 | 44% n=111 | 36% n=111 | 43% n=111 | 33% n=111 | 43% | 66% n=111 | 68% n=111 |
| BITB58 | too few photos n=1 | too few photos n=1 | too few photos n=1 | too few photos n=1 | 67% | too few photos n=1 | too few photos n=1 |
| BIEA24.5 (not in the regional mean) | too few photos n=5 | too few photos n=5 | too few photos n=5 | too few photos n=5 | — | too few photos n=5 | too few photos n=5 |
| BITB34.5 (not in the regional mean) | too few photos n=3 | too few photos n=3 | too few photos n=3 | too few photos n=3 | — | too few photos n=3 | too few photos n=3 |
n under each value is the number of photographs that method scored at that dive site. ⚠ marks a cell that is not an independent check. * marks a value resting on only 10–19 photographs, which is less certain.
Reference: IN-WATER DIVER TRANSECT, independent of the imagery (Mayfield & Dempsey 2026, Oceans 7:1). Denominator: line/point intercept along the transect; not a photo-point denominator. Source: the mean of all of each station's transects (Living Oceans Foundation per-transect benthic data); the published station values, which weight each depth equally, are in Mayfield & Dempsey 2026, Oceans 7:1, suppl. S1 (formal 38.7% cover / 30.5% bleaching, tourist-diver 35.1% / 31.8%) For all 104 dive sites in the comparison: ⚠ The reference here is NOT the same instrument as at Mauritius, Oman, Kenya, or the Red Sea. 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 the mean of all of each station's own transects in the expedition's per-transect benthic data.
Nearby external survey stations
9 independent survey records within 5 km of a site in this region (each record counted once; 5 lines, and a line that pools several records says how many).
- Sheppard et al. (2008) — Great Chagos Bank (2006): 41% hard coral cover, 0.42 km from Chagos Archipelago - Great Chagos Bank West (BITB27) (5 records)
- XL Catlin Seaview Survey — transect 36001 (2015): 6.3% hard coral cover, 1.05 km from Chagos Archipelago - Great Chagos Bank West (BIDI14)
- XL Catlin Seaview Survey — transect 36002 (2015): 25% hard coral cover, 0.26 km from Chagos Archipelago - Great Chagos Bank West (BIDI09)
- XL Catlin Seaview Survey — transect 36003 (2015): 13% hard coral cover, 0.30 km from Chagos Archipelago - Great Chagos Bank West (BIEA24)
- XL Catlin Seaview Survey — transect 36004 (2015): 21% hard coral cover, 0.26 km from Chagos Archipelago - Great Chagos Bank West (BITB40)
All images from Coral Reef Diagnostics. Data are from the Khaled bin Sultan Living Oceans Foundation Global Reef Expedition, Coral Reef Diagnostics, XL Catlin Seaview Survey (University of Queensland), and Sheppard et al. (2008).
© Coral Reef Diagnostics.
References
- Souter D, et al. (eds) (2021) Status of Coral Reefs of the World: 2020. International Coral Reef Initiative / Global Coral Reef Monitoring Network. [PDF]
- Spalding MD, et al. (2001) World Atlas of Coral Reefs. University of California Press, Berkeley. [PDF]
- Wilkinson C (2006) Status of coral reefs of the world: summary of threats and remedial action. In: Côté IM, Reynolds JD (eds) Coral Reef Conservation. Cambridge University Press, Cambridge. [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
- 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