Chagos Archipelago - Peros Banhos (BIPB110)

Setting

BIPB110 is a leeward lagoonal pinnacle reef in the eastern Peros Banhos lagoon (massive coral dominated on the LOF habitat map), dived to 30.7 m on 30 April 2015 (station CTD-cast midpoint 30.6°C).

General benthic features

It is an Acropora reef first and foremost. Acropora holds 19% of the benthos — 47% of all coral recorded (e.g., Image 21) — with Porites second at 9.1%, then Pocillopora 2.6%, Echinopora and Montipora 1.5% each, Favia and Symphyllia 1.3% each, Pavona 0.9%, Stylophora 0.7%, Leptastrea 0.6%, Goniastrea 0.5%, and Astreopora, Herpolitha, Lobophyllia, and Seriatopora 0.3% each.

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Below that sits an eight-genus tail of 0.2% or less: Cyphastrea, Favites, Galaxea, Goniopora, Millepora, and Platygyra (0.2% each), and Montastrea and Psammocora (0.1% each). Turf holds 14% of the benthos, bare substrate 12%, crustose coralline algae 7.8%, non-coral invertebrates 6.1%, erect algae 3.4%, and macroalgae 1.6%. Coral cover declines steadily with depth while the assemblage reorganizes completely. D2 carries 50% coral led by Acropora at 25% with Porites at 17%; D3 holds 38% with Acropora still dominant at 18%; D4 falls to 37% and Symphyllia rises to 9.0% behind Acropora's 16%; and D5 drops to 32% and Acropora is displaced entirely — Favia leads at 9.0%, then Echinopora 8.0%, Acropora 6.0%, and Herpolitha 3.0%, with algal cover jumping to 60%. Genus richness peaks in the middle at 17 codes on D3 against six on both D4 and D5. The site-level figures therefore average a shallow Acropora reef onto a deep faviid-and-Echinopora one. Broad plates project over lower colonies, corymbose and branching forms fill intervening spaces, and massive colonies form large rounded buttresses (e.g., Image 10, Image 15, Image 16, Image 19, Image 42, Image 48).

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In one frame, several pale tables overlap like shelves above darker plates and encrusted framework (e.g., Image 5).

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Several more frames show the same multi-tiered architecture at wider scale, with live colonies distributed across an irregular surface rather than concentrated in one isolated patch (e.g., Image 8, Image 17, Image 31, Image 32, Image 39).

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Two frames establish a mixed hard-bottom mosaic with sand-filled gaps (e.g., Image 2, Image 12) and another records the broader broken relief (e.g., Image 49).

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Sand occupies channels and pockets but does not break the continuity of coral habitat along much of the photographed route (e.g., Image 3).

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Encrusting red and purple surfaces are common on exposed framework (e.g., Image 7, Image 11), small rounded and meandroid colonies occur beside the larger tables (e.g., Image 29), and reef fishes occupy both the water column and crevices.

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Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• BIPB110 is a coral-abundant, architecturally complex reef with 23 coral genera at 42% coral cover (LOF transects).
• Transect mean 42 ± 4.1% SE (n = 11 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean, and the published station value, which weights each depth equally, is 39% (Mayfield & Dempsey 2026, Oceans, suppl. S1).
• Formal surveys give 42% coral, 40% algae, and 6.1% non-coral invertebrates, the coral 50% Acropora in the shallows (D2) and led by Favia and Echinopora at D5.

Stressors

Bleaching is unmistakable and affects more than one growth form. One frame shows a compact branching colony almost uniformly white while retaining intact fine branch structure (e.g., Image 25).

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Another frame contains large table-like colonies with equally stark loss of pigmentation (e.g., Image 40, Image 47), and additional pale branches and plates recur across the middle of the sequence (e.g., Image 44).

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The most dramatic condition feature is the enormous massive colony followed across a run of consecutive frames (e.g., Image 13, Image 24).

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One view shows a partly pigmented tan surface (e.g., Image 9), whereas two others show extensive white tissue interspersed with broad dark red-brown areas (e.g., Image 20, Image 30).

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Another view demonstrates the colony's exceptional size and the spatial separation between the pale upper surface and the darker areas (e.g., Image 41).

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The white areas are consistent with severe bleaching. The dark areas appear established and algal or microbial overgrowth is plausible, but the stills do not show an advancing lesion margin, so they are described as areas of apparent prior tissue loss rather than assigned a disease diagnosis. Anderson's sampling sheet records two colonies sampled here: a Pocillopora acuta by field call (CHPd150, 30.7 m), the only one seen at the site, healthy but with very pale branch tips, which were sampled, and a healthy Seriatopora hystrix (ChSe156, 28.7 m). Pocillopora acuta colonies from this archipelago were analyzed in Thomas et al. (2026, Global Ecology and Biogeography 35:e70305, https://doi.org/10.1111/geb.70305). The Living Oceans Foundation transects here recorded 2.5% cyanobacteria and 0.9% recently dead coral.

Fish and other fauna

A shark rested beneath an overhang with golden trevally (e.g., Image 37, Image 43).

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One frame under the same ledge shows a resting sea turtle, its patterned scutes and scaled head compatible with a hawksbill (e.g., Image 18).

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Comparisons with other data

Apart from the Living Oceans Foundation survey shown here, we found no other surveys at this site as of 2026. If you would like to share yours, please email us.

Other notes

Reef type follows the LOF habitat map: the pin sits inside 'lagoonal pinnacle reefs - massive coral dominated' in the eastern lagoon; a lagoon pin has no rim facing. Anderson's field sheet (LOF fellowship 2016 workbook) records 'lagoonal channel reef', 'leeward'; the expedition's 933-site table classes the station as 'protected' (patch reef).