Chagos Archipelago - Peros Banhos (BIPB112)

Setting

BIPB112 is a windward fore reef slope on the north-east rim of Peros Banhos, outside the lagoon, dived to 30.9 m on 2 May 2015 (e.g., Image 13).

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General benthic features

Genus richness is high at 30 genera, with Acropora holding 56% of all coral and a nineteen-genus tail sharing barely 1.8 points of benthos.

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Transects recorded 46% coral against 44% algae on hard, clean substrate where sediment does not settle, turf-plus-sediment reaching only 0.9% (e.g., Image 1, Image 5, Image 7, Image 12, Image 18, Image 19).
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• Transect mean 46 ± 4.3% SE (n = 16 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 45% (Mayfield & Dempsey 2026, Oceans, supplemental S1).
• The depth profile is an almost complete handover: cover peaks at 57% at the shallowest stratum, where Acropora alone holds 75% of the coral, then declines monotonically to just 13% of the coral at the deepest, where Porites (38%) and Montipora (22%) take over.
• Live hard coral measured on the in situ benthic transects of the LOF BIOT-1 expedition (the mean of all of this station's transects), against total algal cover (all algal groups) of 44% of the benthos.
• Image-based estimates (DINOv3, CoralSCOP, and Claude) are listed in the method table for comparison only; the transect figure is this site's cover value.

Stressors

Bleaching here reads 38% under the second CoralNet training run; this second-run value is the published figure (Mayfield & Dempsey 2026, suppl. S1). The photographs sit with the high end: a meter-scale tiered table gone uniformly bone-white beside pigmented neighbors, a cluster of four or more white tables, a completely white plate next to a partially bleached one (e.g., Image 2, Image 3, Image 8, Image 9, Image 11, Image 16).

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No disease, predation, or crown-of-thorns was seen in the photographs, though the sampling sheet notes some purple lesions on one colony (ChJo297); a school of trevally-type jacks was photographed off the wall (e.g., Image 6), and Anderson saw and filmed a whale shark on this dive (from 10–20 m away, per the sheet), which none of the stills captures.

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Five of the nine colonies Anderson sampled here were 80% or more bleached (see Dive record below). The Living Oceans Foundation transects here recorded 0.1% cyanobacteria and 0.1% 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 2 May 2015 entered the water at 10:47 and lasted 54 minutes, to a maximum depth of 30.9 m (the field sheet); the notes describe a deep, steep, clear fore-reef wall with the most diverse coral at 15–25 m, scoured shallows at 10 m with some bleaching (mostly pocilloporids), a current that picked up during the dive, a school of jacks, and a 7–8 m whale shark, filmed from 10–20 m away. Anderson sampled four Seriatopora hystrix colonies, found only below 20 m: ChSe171 (10:54, 28.8 m; darkly pigmented, some algal overgrowth), ChSe172 (11:00, 30.4 m; large and healthy), ChSe173 (11:03, 25.4 m; 80% bleached, with blue-green fluorescence), and ChSe174 (11:08, 21 m; more than 95% bleached and being smothered by cyanobacteria). For a collaborator Anderson sampled five pocilloporids: ChJo293 (likely Pocillopora verrucosa; 11:14, 15.9 m; more than 90% bleached), ChJo294 (Pocillopora sp.; 11:20, 13.8 m; healthy), ChJo295 (Pocillopora sp.; 11:23, 11.9 m; more than 95% bleached), ChJo296 (likely P. verrucosa; 11:30, 10.5 m; 80% bleached, with totally bleached pocilloporids nearby), and ChJo297 (Pocillopora sp.; 11:35, 9.5 m; large and healthy, some purple lesions, bleached colonies nearby). 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

Anderson's field sheet (LOF fellowship 2016 workbook) records 'fringing reef', 'windward'; the LOF habitat map puts the pin 67 m from 'deep fore reef slope' on the north-east rim, which faces north-east, side-on to both the southeast trades and the northwest monsoon; the expedition's 933-site table classes the station as 'exposed' (fringing reef). The aspect printed above is the field sheet's 'windward', because the station's GPS position does not settle the aspect (relative to the prevailing southeast trade winds, it reads side-on from the atoll's center and leeward from the nearest reef edge); the habitat map's side-on reading is noted above for comparison.