Chagos Archipelago - Great Chagos Bank West (BICC50)

Setting

BICC50 is a submerged bank reef inside the Central Chagos lagoon at 20.0 m under intermediate exposure, surveyed 25 March 2015 (the photo archive files it as BITB50).

General benthic features

The algal budget is 33.2% sediment-laden turf and 14.6% erect algae, while coralline algae is all but absent at 2.9%, second-lowest of 109. Only 14 genera were recorded, and Acropora, Montipora, and Porites hold 82% of the coral between them — though even the leading genus covers under 5% of the benthos, so this ranks which taxa are least scarce.

Coral cover

It is one of the lowest-cover sites in the archipelago: 12.1% coral against 57.9% algae, 102nd of 109 Chagos sites for cover and 10th for algae, with a further 24.3% bare substrate. The depth structure is inverted: the deeper stratum carries 18.78% coral against 5.33% shallower, the same genus order at both. Unusually, the image methods agree here — CoralNet 13.9%, Coralscapes 12.8% against 12.1% — a property of the low-cover regime, not interchangeability.

Stressors

Published bleaching is 24.2%, 3rd of 98 on the site table's Mean(%bleaching) column (the first CoralNet training run, not the canonical % bleaching (2nd training) column), but that figure is unsafe here: 25 of 26 bleached point labels fall in four macro frames of a pair of mantle-extended gastropods whose white mantles were read as coral (e.g., Image 3, Image 4), the Coralscapes masks report essentially zero bleached area, and the wide frames show a flat, turf-veneered plain with no bleaching field (e.g., Image 1).

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Fish and other fauna

Two shark passes were logged, no disease or crown-of-thorns (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.