Chagos Archipelago - Salomons Island (BISA93)

Setting

BISA93 is an exposed windward emergent forereef on the seaward side of Salomon at 30.4 m, surveyed 25 April 2015.

General benthic features

Genus richness is the site's strength: 34 genera, 5th-highest of the 109, including the Indian Ocean endemic Ctenella, on a reef where Porites alone holds 49% of all coral (e.g., Image 3, Image 4).

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Coral cover

Formal transects recorded 39.1% coral against 34.9% algae — 56th of 109 Chagos sites for cover, 71st for algae, mid-pack on both — with bare substrate very low at 5.5% and non-coral invertebrates unusually high at 20.5%, visible in the imagery as gorgonian sea fans, black whip corals, and barrel sponges that the transect protocol never resolves to taxon (e.g., Image 2).

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The depth profile is a sharp peak and a collapse — 38.0% coral shallow, a 58.6% second stratum where Porites reaches 36.7% of the benthos, then 39.4% at the most genus-diverse band with 26 genera, then a fall to 20.25% at the deepest, where algae takes 40.8%, bare substrate 17.1%, and Acropora is essentially gone at 0.45%. Image methods read 21 to 22 points below the transects (CoralNet 18.3%, Coralscapes 17.1%) and should not be averaged with them. Coral cover: 39%. 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 34.9% 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 39.1% · CoralNet points 18.3% · Coralscapes masks 17.1% (28 frames). These products have different sampling footprints and denominators and should not be averaged.

Stressors

Bleaching on the canonical % bleaching (2nd training) column is 11.90%, 30th of 110 dives, the worst quintile, and both runs agree — yet all 28 frames were reviewed and the photographs read considerably worse than 12%: colony-scale whitening appears in a substantial majority of them, including bone-white colonies beside fully pigmented neighbors under identical lighting and a massive dome bleached across exactly half its surface (e.g., Image 1, Image 5).

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Pale plating Acropora and old exposed skeleton can inflate that impression, but not those cases. No crown-of-thorns, disease band, or fresh predation scar in any frame.

Fish and other fauna

Bluefin trevally were photographed hunting baitfish and a grazing school of thirty-plus parrotfish crossing the reef.

Comparisons with other data

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