Chagos Archipelago - Great Chagos Bank West (BICC51)

Setting

BICC51 is a submerged bank reef inside the Central Chagos lagoon at 29 m under intermediate exposure, surveyed 25 March 2015.

General benthic features

Its defining number is not its coral but its algae: at 70.0% algal cover it is the single most algae-dominated of the 109 Chagos sites, 1st of 109, against 15.4% coral, which ranks 98th (e.g., Image 1).

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Nearly half that algal budget is sediment-laden turf at 31.6% of the benthos, with coralline algae at 20.8%, while clean fleshy turf is just 3.0% — a figure ranking 104th of 109 that would invert the site's real standing if quoted alone (e.g., Image 2).

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The 18 genera divide the small coral budget unusually evenly, no genus reaching a quarter of it: Pocillopora 25%, Acropora 21%, Porites 20%, Stylophora 12%.

Coral cover

Cover peaks at mid-depth, 12.7% to 20.2% and back to 13.3%, the lead genus changing hands at every station — Acropora and Pocillopora tied shallow, Pocillopora clear at mid-depth, Porites deepest — while algal cover never drops below 67.8% anywhere on the profile. No CoralNet or Coralscapes product exists for this site, so the transect figure is the only cover number it has. Coral cover: 15%. 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 70% of the benthos. The transect figure is this site's authoritative cover value; no image-derived product overrides it.

Stressors

Published bleaching is 4.5%, ranked 74th 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 19-frame review found no unambiguous pallor, no disease, predation, or crown-of-thorns.

Fish and other fauna

A whitetip reef shark rests under a plating colony across three frames, and the schooling fish traffic is markedly out of proportion to the coral (e.g., Image 3, Image 4).

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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.