Chagos Archipelago - Peros Banhos (BIPB67)

Setting

BIPB67 is a leeward fore reef slope on the west rim of Peros Banhos (from its position on the atoll's northwest side relative to the prevailing southeast trade winds), dived to 30.7 m on 16 April 2015 (station CTD-cast midpoint 30.1°C); Anderson's notes describe a beautiful, steep wall with mild current and impressive fish schools.

General benthic features

Acropora and Porites lead the assemblage at roughly 16% of the benthos each, though the balance shifts strongly with depth, from an Acropora-dominated shallow zone to Porites-dominated deeper ground. The reef alternates between dense multi-genus coral thickets and stretches of low-cover pavement and rubble, with a gray reef shark and a large grouper among the fish recorded (e.g., Image 1).

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Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• 46%, against 38% algal cover (LOF transects).
• Transect mean 46 ± 3.1% SE (n = 19 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 42% (Mayfield & Dempsey 2026, Oceans, suppl. S1).

Stressors

Published bleaching is 4.9% of coral (CoralNet analysis of the survey images; Mayfield & Dempsey 2026, suppl. S1). The photographs show white massive colonies among pigmented neighbors (e.g., Image 15, Image 35) and broken table plates lying flat on the rubble (e.g., Image 5), matching Anderson's note of storm damage at 10–12 m.

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The sheet records some bleached branches on the only Seriatopora colony seen at the site (ChSe70) and 5% bleaching on a sampled pocilloporid (ChJo176) (see Dive record below). The Living Oceans Foundation transects here recorded 0.1% cyanobacteria and 0.2% 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. If you would like to share yours, please email us.

Dive record

Anderson's dive on 16 April 2015 entered the water at 10:19 and lasted 61 minutes, to a maximum depth of 30.7 m (the field sheet); the notes describe a beautiful, steep wall with high coral cover, impressive fish schools, and mild current, with some storm damage at 10–12 m beside areas of high acroporid cover. Anderson sampled the only Seriatopora hystrix colony seen at the site, ChSe70 (collected 10:30 at 26 m; an encrusting mat from 26 to 27 m with some bleached branches; the healthy section was sampled), and three pocilloporid colonies for a collaborator: ChJo174 (Pocillopora meandrina or P. eydouxi; 10:43, 15.2 m; odd blue marks, though likely healthy), ChJo175 (likely P. verrucosa; 10:57, 10.2 m; healthy, with a green fluorescent hue), and ChJo176 (Pocillopora sp.; 11:05, 11 m; 5% bleached, candelabrum morphology). The notes record no P. acuta or P. damicornis 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 follows the LOF habitat map: the pin lies 42 m from 'deep fore reef slope' on the atoll's northwest rim (fore reef slope). Anderson's field sheet (LOF fellowship 2016 workbook) records 'fringing reef', 'windward'; the expedition's 933-site table classes the station as 'intermediate' (fringing reef). The rim here faces west to west-northwest: windward of the northwest monsoon (December–March), leeward of the April–November southeast trades; Anderson's sheet label is 'windward'. The aspect shown, 'leeward', comes from the station's GPS position relative to the prevailing wind: the pin lies on the northwest side of Peros Banhos, about 162° off the prevailing southeast trades.