Chagos Archipelago - Salomons Island (BISA91)

Setting

BISA91 is a back reef inside Salomon lagoon, windward from its position on the east side of Salomon atoll relative to the prevailing southeast trade winds (leeward on Anderson's field sheet), surveyed 24 April 2015 on a dive to 21.3 m (station CTD-cast midpoint 30.8°C).

General benthic features

Across 28 genera the site average looks even, three genera at 11% to 12% of the benthos with no clear leader — but that evenness is an averaging artifact, and it is the site's real finding: each depth stratum is dominated by a different genus. The shallowest is Acropora ground at 23% of the benthos, the next hands over entirely to Goniopora at 21%, the third to Porites at 20%, and the single deepest transect is 26% Montipora (77% of its coral) with only nine genera; half of the site's Montipora figure comes from that one transect and 63% of its Acropora from two. Only Lobophyllia is abundant through D1–D3, and it is absent from the single D4 transect.

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Formal transects recorded 57% coral against 34% algae, with turf at 14% of the benthos and non-coral invertebrates very low at 3.5%.
• Transect mean 57 ± 3.9% SE (n = 15 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean, and the published station value, which weights each depth equally, is 52% (Mayfield & Dempsey 2026, Oceans, supplemental S1).
• Live hard coral measured on the in situ benthic transects of the LOF BIOT-1 expedition (the mean of all of this station's transects), against total algal cover (all algal groups) of 34% of the benthos.
• Image-based estimates (CoralNet, DINOv3, CoralSCOP, and Claude) are listed in the method table for comparison only; the transect figure is this site's cover value.

Stressors

Published bleaching is 12% (CoralNet analysis of the survey images; Mayfield & Dempsey 2026, suppl. S1). In the photographs, three frames show unambiguous colony-scale bleaching — a bone-white branching colony beside a pigmented neighbor, a brilliant white massive colony among pigmented ones, and a large polyp-expanded colony pale over most of its living surface. One colony is tan across half its surface and vivid pink across the other with continuous polyp structure between, reading as a chromoprotein response; the rose-pink masses recurring here may be sponges or Lobophyllia; the frames do not settle which (e.g., Image 3, Image 4).

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No crown-of-thorns starfish or disease signs appear in the photographs. Anderson's sampling sheet records 12 colonies sampled here at 4.8–20.2 m: 11 Pocillopora acuta by RFLP; one P. acuta by field call; the condition notes run from healthy to 100% bleached, with some partly dead colonies. Pocillopora acuta colonies from this archipelago were analyzed in Thomas et al. (2026, Global Ecology and Biogeography 35:e70305, https://doi.org/10.1111/geb.70305). The Living Oceans Foundation transects here recorded 0.1% cyanobacteria and 0.1% recently dead coral.

Comparisons with other data

Thriving Oceans surveyed a nearby station (SAL Fouquet Lagoon) in 2015, 2018, and 2021, 0.42 km from the pin; we could not confirm that it is the same reef. Within 5 km, five independent stations recorded station-year means of 9.9–43% hard coral cover between 2006 and 2020; the nearest of these, Lange et al. (2021) at Salomon Atoll, 1.21 km away, read 9.9–43% between 2006 and 2020.

Other notes

Anderson's field sheet records the aspect (LOF fellowship 2016 workbook: 'backreef', 'leeward'); the expedition's 933-site table classes the station as 'protected' (bank reef). The aspect shown, 'windward', comes from the station's GPS position on the east side of Salomon atoll relative to the prevailing southeast trade winds (about 34° off the upwind direction; the reef-edge reading agrees), which takes precedence over slope facing, lagoon shelter, imagery, and field labels. Esri World Imagery (no LOF habitat map covers Salomon atoll; the LOF Chagos habitat map covers only Peros Banhos) puts the pin on the lagoon-side back reef of the eastern island, consistent with the sheet.