Chagos Archipelago - Peros Banhos (BIPB75)

Setting

BIPB75 is an exposed, windward emergent fringing forereef outside Peros Banhos, surveyed 19 April 2015 at 31.0 m.

General benthic features

The assemblage is the departure: across 20 genera, Porites holds 51% of all coral while Acropora, normally the leading genus on an exposed Chagos forereef, manages only 3.0% of the benthos, so the reef's structure is carried by massive mounds rather than tables. Cover almost halves down the profile, from 63.25% at the shallowest transect — where Porites alone is 64% of the coral — to 35.5% and then 33.0%, with Montipora rising to a quarter of the coral at the deepest station.

Coral cover

Formal transects recorded 43.9% coral against a comparatively low 32.8% algae — 38th of 109 Chagos sites for cover, 81st for algae — with coralline algae unusually scarce at 6.8% and non-coral invertebrates taking 17.4% of the benthos. Image methods read lower than the transects — CoralNet 29.6%, Coralscapes 31.4% against 43.9%. Coral cover: 44%. 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 32.8% 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 43.9% · CoralNet points 29.6% · Coralscapes masks 31.4% (9 frames). These products have different sampling footprints and denominators and should not be averaged.

Stressors

Published bleaching is 17.4%, and the top-decile rank of 10th of 98 comes off the site table's Mean(%bleaching) column, the first CoralNet training run rather than the canonical % bleaching (2nd training) column. The photographs back it at colony scale: two fully white plating colonies beside pigmented neighbors, lavender-white branch-tip paling in another frame, a whole brain colony gone pale mauve, plus a deep sand-slope frame of gorgonians, black corals, and sponges that explains the invertebrate reading (e.g., Image 1).

1

No disease or crown-of-thorns was seen.

Comparisons with other data

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