Chagos Archipelago - Peros Banhos (BIPB63)

Setting

A leeward lagoonal pinnacle reef in Peros Banhos (branching coral dominated on the LOF habitat map), dived to 25.8 m on 15 April 2015.

General benthic features

The reef is overwhelmingly a single-genus system: Acropora makes up 91% 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).

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Coral cover and Acropora dominance both fall sharply with depth, giving way in the deepest stratum to a sparse, algae-dominated community of scattered massive corals (e.g., Image 5, Image 9, Image 23, Image 26, Image 30).

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Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Transect mean 56 ± 5.4% SE (n = 15 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 56% (Mayfield & Dempsey 2026, Oceans, suppl. S1).

Stressors

Published bleaching is 2.0% (CoralNet analysis of the survey images; Mayfield & Dempsey 2026, suppl. S1), but several photographs show colony-scale white pallor among the tabular corals (e.g., Image 4, Image 15, Image 20, Image 29, Image 33), and Anderson's sampling sheet records three Seriatopora hystrix colonies more than 90% bleached (ChSe65–ChSe67) and a 20%-bleached pocilloporid (CHPd74).

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The bleaching percentage is a computer vision figure: CoralNet annotation of the informal survey images, not a diver's field estimate (Mayfield & Dempsey 2026, suppl. S1). Anderson's sampling sheet records nine colonies sampled here at 9.5–25.5 m: three Pocillopora acuta and one P. damicornis by RFLP; three Seriatopora hystrix by field call; two Pocillopora sp. sampled for a collaborator (field calls); the condition notes run from healthy to >90% bleached, with some partly dead colonies. 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 0.2% cyanobacteria and no recently dead coral.

Comparisons with other data

Apart from the Living Oceans Foundation survey shown here, we found no other surveys at this site as of 2026. Within 5 km, two independent stations recorded station-year means of 27–44% hard coral cover between 2006 and 2015; the nearest, Sheppard et al. (2008) at Peros Banhos, 2.82 km away, read a mean of 44% in 2006.

Other notes

Reef type follows the LOF habitat map: the pin lies 1 m from 'lagoonal pinnacle reefs - branching coral dominated' inside the lagoon; a lagoon pin has no rim facing. Anderson's field sheet (LOF fellowship 2016 workbook) records 'lagoonal patch reef', 'leeward'; the expedition's 933-site table classes the station as 'protected' (patch reef).