Chagos Archipelago - Salomons Island (BISA103)

General benthic features

The assemblage is broad, with 28 non-zero coral genera. Porites leads at 13.23% of the benthos — 41% of all coral recorded — with the branching component carried by Stylophora at 4.84% and Pocillopora at 3.59%, an unusual pairing for Chagos. Pavona follows at 1.92%, Goniastrea 1.16%, Acropora only sixth at 1.11%, Montipora 1.09%, and Gardineroseris and Favia both at 0.82%. Sixteen further genera fall below 0.5%, including Physogyra, Oulophyllia, Cantharellus, Oxypora, and Hydnophora. Non-coral invertebrates hold 21.1% of the benthos, crustose coralline algae 16.4%, turf 15.3%, and bare substrate 5.3%. Reef architecture is moderate, with colonies set into older consolidated framework and separated by small sand or rubble pockets (e.g., Image 1).

1

Broad views show rounded massive colonies, compact branching clusters, low plates, and encrusted surfaces rather than one continuous canopy (e.g., Image 3, Image 4).

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Two frames are useful for the juxtaposition of branching and massive forms around open substrate, and a later run of frames shows repeated changes in colony scale and relief over a short route. The result is a heterogeneous habitat with many edges and crevices but markedly less vertical layering than the dense channel reef at BIPB110. The photographed benthos includes purple and red encrusting surfaces, brown algal growth, and small mound-forming colonies, all adding texture and microhabitat diversity — the visible counterpart to a 21.1% non-coral invertebrate figure. The photographs show massive, compact branching, and plating forms embedded in encrusted framework with small sand and rubble openings, and bleaching common and conspicuous across multiple frames.

Coral cover

Coral cover is 33%, 70th of the 109 Chagos sites, against 41.2% algae — but published image bleaching is 24.1%, ranking 4th of 98. Coral cover falls by more than half from the shallowest band to the deepest. D2 carries 47.4% — a genuinely coral-abundant shallow reef, with Porites at 25.23% and Stylophora at 7.73%, across 24 genera. D3 drops to 28.6% and Porites collapses to 6.60%, leaving Stylophora (5.88%) and Pocillopora (5.25%) nearly level with it. D4 falls again to 21.4%, with Porites at 7.85% and algal cover at 39.8%. Genus richness declines with cover, from 24 to 22 to 19 codes. The 13.23% site-level Porites figure is therefore dominated by a single shallow transect and should never be quoted as a uniform value. Assemblage composition. Formal surveys give 32.5% coral, 41.2% algae, and 21.1% non-coral invertebrates, the coral Porites-led with a Stylophora–Pocillopora branching component and Acropora only sixth.

Stressors

Bleaching is visually prominent and matches the high published figure. One frame contains several colonies at different degrees of pallor: one central branching colony has white branch ends and light tissue farther inward, while neighbors range from darkly pigmented to nearly white (e.g., Image 2).

2

Another frame shows a large table- or foliose-like colony whose upper surface is coherently white, with intact corallite and plate structure still visible. Additional pale colonies occur in a later run of frames. The recurrence across both wide and close views makes bleaching the most parsimonious reading. Not every pale feature is classified as bleaching. White branch tips can reflect active growth, bright illumination, or normal interspecific color, and some exposed skeleton is already dulled by sediment or overgrowth. The flagged examples were selected because pallor extends broadly across intact tissue and contrasts with nearby pigmented colonies. Small dark points on the large pale table- or foliose-like colony could be attached organizms, sediment, or localized mortality, but they do not justify a disease diagnosis. No crown-of-thorns starfish (COTS) or other corallivores evident.

Fish and other fauna

Several frames show fish close to the substrate, including small damselfish-like and surgeonfish-like silhouettes, but the sequence is not a fish census.

Comparisons with other data

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