Chagos Archipelago - Blenheim (BIBL87)

Setting

BIBL87 is a submerged forereef at Blenheim under intermediate exposure, surveyed 23 April 2015 at 27.4 m.

General benthic features

Its distinction is diversity rather than cover: 36 coral genera, the highest genus richness of all 109 Chagos sites, and no dominant taxon — Acropora leads at just 20% of the coral present, with Porites, Pocillopora, Pavona, and Montipora close behind (e.g., Image 4, Image 6, Image 10, Image 18, Image 20, Image 21, Image 23, Image 25, Image 30, Image 31).

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Coral cover

Formal transects recorded 41% coral cover against 47.1% algae, with noticeably more open and sediment-covered ground than its neighbor BIBL86 (e.g., Image 8, Image 14, Image 17, Image 22, Image 36, Image 39).

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The three depth transects peak at 53% cover at mid-depth, precisely where the assemblage is most even, between an Acropora-dominated shallow station and a Porites-led deep one under the highest algal cover of the profile. Image-based methods read this reef 22–25 points lower than the transects (CoralNet 18.6%, Coralscapes 16.0%); the three are not interchangeable and should not be averaged (see the full report).

Stressors

Published bleaching is 9.6%, and the photographs record pale-to-white table colonies at close range over a reef alternating between open crusted pavement and branching-and-table habitat (e.g., Image 1, Image 2, Image 7, Image 13, Image 15, Image 19, Image 27, Image 29, Image 35).

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No crown-of-thorns or disease signs were identified in the 35 stills reviewed. The bleaching percentage is a computer vision figure — CoralNet annotation of the informal survey images, not a diver's field estimate — and human-vs-model agreement is weaker for bleaching (r = 0.40) than for coral cover (r = 0.72).

Comparisons with other data

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