Chagos Archipelago - Peros Banhos (BIPB114)

Setting

BIPB114 is an exposed, windward emergent fringing forereef outside Peros Banhos; the published survey-depth cell is blank, so the reef carries no depth on record (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%, unusual for a Chagos forereef (e.g., Image 19, Image 46).

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Cover falls monotonically with depth, 56.7% to 38.8% to 23.2%, Porites leading every transect while Acropora thins to 0.72% at the deepest.

Coral cover

Formal transects recorded 39.6% coral against 33.8% algae — 54th of 109 Chagos sites for cover — across 31 genera, the 14th-highest genus count of the 109, with more than a quarter of the reef neither coral nor algae (12.8% bare substrate, 13.9% invertebrates) (e.g., Image 4, Image 12, Image 24, Image 25, Image 40).

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The image cover figures (CoralNet 19.6%, Coralscapes 18.9%) pool both dives. Coral cover: 40%. Live hard coral measured on the in situ benthic transects of the LOF BIOT-1 expedition (Mayfield & Dempsey 2026, Oceans, supplemental S1), against algal cover of 33.8% of the benthos. The transect figure is this site's authoritative cover value; no image-derived product overrides it. Across methods the same reef reads: transects 39.6% · CoralNet points 19.6% · Coralscapes masks 18.9% (41 frames). These products have different sampling footprints and denominators and should not be averaged.

Stressors

The site was dived twice on consecutive days and both were scored: under the canonical % bleaching (2nd training) column it reads 22.6% on 2 May and 22.7% on 3 May, indistinguishable across 15 hours, as an already-established bleaching state should be. The site table's Mean(%bleaching) gives 2.5% for the same dive, the first training run and not canonical. The photographs support the higher figure: 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 41, Image 51).

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

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No crown-of-thorns or disease.

Comparisons with other data

No prior survey data from this site. If you would like to share yours, please email us.