Chagos Archipelago - Salomons Island (BISA84)

Setting

BISA84 is a leeward fringing fore reef outside Salomon atoll (from its position on the northwest side of Salomon atoll relative to the prevailing southeast trade winds; windward on Anderson's field sheet), surveyed 22 April 2015 on a dive to 21.8 m.

General benthic features

Across 25 genera, Acropora (54% of all coral present) and Porites (22%) hold three-quarters of the coral between them.

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Formal transects recorded 49% coral cover against 42% algae, but the defining number is its bleaching: 34%.
• Transect mean 49 ± 5.3% SE (n = 17 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 49% (Mayfield & Dempsey 2026, Oceans, suppl. S1).
• Coral cover rises from the shallowest stratum (35%) to mid-depth (57%), where Acropora alone accounts for 70% of the coral, before Porites takes the lead at the deepest stratum.

Stressors

White colonies show in five to six of the 10 frames: stark-white branching colonies beside pigmented massive and meandroid colonies (e.g., Image 6, Image 7, Image 10) and white plating colonies beside tan ones (e.g., Image 3, Image 4), over a table- and branch-dominated reef with local sand-and-rubble breaks (e.g., Image 1, Image 2).

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No crown-of-thorns or disease signs were identified in any of the 10 frames. The bleaching percentage is a computer vision figure: CoralNet annotation of the informal survey images, not a diver's field estimate (Mayfield & Dempsey 2026, suppl. S1). All seven colonies Anderson sampled here were partly or fully bleached (see Dive record below). The Living Oceans Foundation transects here recorded 0.1% cyanobacteria and 0.1% recently dead coral.

Comparisons with other data

Perry et al. (2015) surveyed a nearby station (Ile Anglaise north, Salomon) in March 2015, 0.20 km from the pin. Within 5 km, seven independent stations recorded station-year means of 6.8–63% hard coral cover between 2006 and 2020; the nearest of these, Lange et al. (2021) at Salomon Atoll, 0.54 km away, read 6.8–63% between 2006 and 2020.

Dive record

Anderson's afternoon dive on 22 April 2015 entered the water at 15:21 and lasted 53 minutes, to a maximum depth of 21.8 m (the field sheet); the notes describe a “beautiful reef from 20 m and below, mostly bleached and dead/dying corals at 15 and above,” with most of the seriatoporids bleaching and no P. acuta at the site. Anderson sampled six Seriatopora hystrix colonies, all but perhaps five to ten of those seen: ChSe105 (collected 15:40 at 22.0 m; neon-green fluorescent, likely 100% bleached or even dead), ChSe106 (15:44, 21.3 m; 50% bleached, with very thin branches; the healthy part was sampled), ChSe107 (15:47, 19.6 m; neon green, small, unsure if alive), ChSe108 (15:53, 19.2 m; neon-green fluorescent, 100% bleached, likely still alive), ChSe109 (15:59, 19.9 m; more than 90% bleached, pigmented only at the branch bases), and ChSe110 (16:04, 19.6 m; more than 90% bleached, pigmented in the interior, with a slight green fluorescent hue). For a collaborator Anderson also sampled ChJo220 (Pocillopora sp., field call P. verrucosa; 16:10, 11.7 m; badly bleached, only the bottom 20% pigmented); the note for it records that most corals at the site were badly bleached. 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).

Other notes

Anderson's field sheet records the aspect (LOF fellowship 2016 workbook: 'fringing reef', 'windward'); the expedition's 933-site table classes the station as 'intermediate' (fringing reef). Esri World Imagery (no LOF habitat map covers Salomon atoll; the LOF Chagos habitat map covers only Peros Banhos) puts the pin about 100 m off the outer reef of the long northwest island, facing northwest: windward for the northwest monsoon winds (about November to March) and leeward for the southeast trades (about April to November); Anderson's sheet label ('windward') is reported for the record. The aspect shown, 'leeward', comes from the station's GPS position on the northwest side of Salomon atoll relative to the prevailing southeast trade winds (about 177° off the upwind direction; the reef-edge reading agrees), which takes precedence over slope facing, lagoon shelter, imagery, and field labels.