Chagos Archipelago - Peros Banhos (BIPB76)

Setting

BIPB76 is an exposed emergent fringing forereef outside Peros Banhos at 21 m, surveyed 19 April 2015, and two numbers define it.

General benthic features

Across 18 genera, Porites holds 38% of the coral and Acropora 28%. Down the profile cover falls by more than half, 54.5% to 32.2% to 21.0%, and Acropora vanishes as it goes — 28.0% of the benthos at the shallowest station, 2.6% at the next, zero at the deepest, where only four genera are recorded at all. The photographs explain both patterns: below the antipatharian-studded upper slope lies an extensive field of large, intact but dead tabular Acropora plates, coated in turf-and-sediment film rather than coralline crust (e.g., Image 2, Image 4).

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Coral cover

Formal transects recorded 35.9% coral against 27.3% algae, but coralline algae is only 2.4% of the benthos — the lowest of all 109 Chagos sites — while fleshy turf is 16.95%, 11th-highest, with bare substrate at 17.9% and non-coral invertebrates at 19.0%. Image methods read some 19 points below the transects (CoralNet 17.0%, Coralscapes 17.1%). Coral cover: 36%. 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 27.3% 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 35.9% · CoralNet points 17% · Coralscapes masks 17.1% (21 frames). These products have different sampling footprints and denominators and should not be averaged.

Stressors

Published bleaching is 22.0%, 6th of 98 on the site table's Mean(%bleaching) column, the first CoralNet training run rather than the canonical % bleaching (2nd training) column — and at least seven frames carry bone-white tables and branching colonies beside fully pigmented neighbors, so the imagery confirms rather than merely permits the figure (e.g., Image 3).

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One encrusting colony with a white band running into dead algal surface could not be resolved between tissue loss and bleaching followed by mortality. No crown-of-thorns or diagnostic disease sign was seen.

Comparisons with other data

No independent survey was made at this exact site; the nearest ones are listed in the table below.