Chagos Archipelago - Peros Banhos (BIPB66)

Setting

BIPB66 is a back-reef rubble channel on the windward west rim of Peros Banhos (back reef, rubble dominated, on the LOF habitat map), dived to 20.9 m on 16 April 2015 in a strong current.

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 5), dense gorgonian sea fan stands, and abundant sea urchins, plus one small coral colony showing clear localized partial bleaching (e.g., Image 7).

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One of the three pocilloporids Anderson sampled was 30% bleached (see Dive record below).

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Coral cover is only 7.8%, against a much higher 54% algal cover (mostly crustose coralline algae and turf rather than fleshy macroalgae); published image bleaching is 6.3%.
• Transect mean 7.8 ± 2.5% SE (n = 5 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 7.0% (Mayfield & Dempsey 2026, Oceans, suppl. S1).
• 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).

Stressors

The Living Oceans Foundation transects here recorded 0.2% cyanobacteria and no recently dead coral.

Fish and other fauna

A manta ray was photographed cruising over the site (e.g., Image 2, Image 3, Image 4); Anderson's notes also record a nurse shark and two marble rays on the dive.

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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. Within 5 km, one independent station, Sheppard et al. (2008) at Peros Banhos, 4.31 km away, read a mean of 44% in 2006.

Dive record

Anderson's dive on 16 April 2015 entered the water at 08:28 and lasted 36 minutes, to a maximum depth of 20.9 m (the field sheet); the notes describe a raging current over a very gradual, low-relief slope with low coral cover, and the dive ended early, though not before seeing a nurse shark, two marble rays, and a manta ray (the second of the trip). Anderson sampled three pocilloporid colonies for a collaborator: ChJo171 (likely Pocillopora verrucosa; collected 08:34 at 20.3 m; large and healthy, among the most common corals at the site), ChJo172 (likely P. verrucosa; 08:38, 19.3 m; 30% bleached), and ChJo173 (Pocillopora sp.; 08:54, 16.0 m; large and overall healthy, with some pale or white branches). The notes record no Pocillopora damicornis, P. acuta, or Seriatopora at the site. 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).

Other notes

Reef type and aspect follow the LOF habitat map: the pin sits inside 'back reef - rubble dominated' in a channel through the west rim. Anderson's field sheet (LOF fellowship 2016 workbook) records 'channel reef', 'windward'; the expedition's 933-site table classes the station as 'intermediate' (channel reef). The rim here faces west to west-northwest: windward of the northwest monsoon (December–March), leeward of the April–November southeast trades; the printed 'windward' is Anderson's sheet label.