Chagos Archipelago - Peros Banhos (BIPB114)

Setting

BIPB114 is a windward fore reef slope on the north-east corner of Peros Banhos, facing southeast into the trades, with dives here on 2 May 2015 (to 26.7 m) and 3 May (to 31 m) (e.g., Image 16, Image 20, Image 33, Image 45).

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General benthic features

Its defining feature is that Porites holds 61% of all coral while Acropora is only fourth at 5.5% of the coral (e.g., Image 19, Image 46).

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Cover falls monotonically with depth, 57% to 39% to 23%, Porites leading every stratum while Acropora thins to 0.7% of the benthos (3% of the coral) at the deepest.

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Transects recorded 43% coral against 33% algae across 31 genera, with nearly a quarter of the reef neither coral nor algae (9.9% bare substrate, 13% invertebrates) (e.g., Image 4, Image 12, Image 24, Image 25, Image 40).
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• Transect mean 43 ± 2.8% SE (n = 30 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 40% (Mayfield & Dempsey 2026, Oceans, supplemental S1).
• 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 33% of the benthos.
• Image-based estimates (CoralNet, DINOv3, CoralSCOP, and Claude) are listed in the method table for comparison only; the transect figure is this site's cover value.

Stressors

The site was dived twice on consecutive days and both dives were analyzed: published bleaching is 22.6% on 2 May and 22.7% on 3 May (CoralNet analysis of the survey images; Mayfield & Dempsey 2026, suppl. S1). The photographs show what that looks like: a fully white corymbose colony beside a pigmented brain colony under one strobe, a survey line laid directly across a stark-white plate, white branching colonies scattered through frame after frame — a serious, broadly distributed but minority signal on a reef whose Porites was largely still pigmented (e.g., Image 9, Image 10, Image 51).

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A host anemone with pale tentacles and resident anemonefish was also photographed (e.g., Image 31, Image 52).

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No crown-of-thorns or disease. Anderson's sampling sheet records 10 colonies sampled here at 11.0–26.2 m: eight Pocillopora sp. and two P. verrucosa sampled for a collaborator (field calls); the condition notes run from healthy to 95% 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 0.1% 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.

Other notes

Reef type and aspect follow the LOF habitat map: the pin sits inside 'deep fore reef slope' on the north-east corner of the atoll, where the slope faces southeast, windward of the southeast trades; the sheet agrees. Anderson's field sheet (LOF fellowship 2016 workbook) records 'fringing reef', 'windward'; the expedition's 933-site table classes the station as 'exposed' (fringing reef).