Chagos Archipelago - Great Chagos Bank West (BICC35)

Setting

BICC35 is a submerged lagoonal bank reef in Central Chagos, forereef aspect under intermediate exposure at 29.3 m, surveyed 20 March 2015.

General benthic features

That gray carbonate film, not fleshy weed, is what 54% algal cover means here (e.g., Image 3).

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Unusually for Chagos, Acropora does not lead: across 18 genera Porites holds 28% of the coral and Pocillopora 21%, Acropora third at 16%.

Coral cover

Formal transects recorded 13.8% coral against 53.9% algae — 100th of 109 Chagos sites for cover, 16th for algae — but the composition of the ground is the story: coralline algae is almost absent at 3.78%, 106th of 109, while turf-plus-sediment takes 25.6%, erect algae 18.3%, and bare substrate 22.4%. The two depth strata carry near-identical cover, 13.3% and 14.2%, yet algae falls from 67.8% to 40.0% between them and the genus order inverts, Acropora leading the shallower and dropping to sixth in the deeper. Image methods read 4-5 points below the transects (CoralNet 9.1%, Coralscapes 9.5%). Coral cover: 14%. 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 53.9% of the benthos. The transect figure is this site's authoritative cover value; no image-derived product overrides it.

Stressors

Published bleaching is 9.0%, 36th of 98 on the site table's Mean(%bleaching) column, the first CoralNet training run rather than the canonical % bleaching (2nd training) column — and the photographs neither confirm nor dismiss it: one colony shows textbook white branch tips over pigmented bases, another is stark white but may be recent death, so bleached individuals were present in March, yet 9% of coral is far more than 19 frames show (e.g., Image 1).

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No disease, predation, or crown-of-thorns.

Fish and other fauna

The vertebrate fauna is the standout: two gray reef sharks, a hawksbill-type turtle, a massed acanthurid aggregation (e.g., Image 2).

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Comparisons with other data

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