Chagos Archipelago - Great Chagos Bank West (BICC35)

Setting

BICC35 is a submerged lagoonal bank reef in Central Chagos, leeward on Anderson's field sheet, surveyed 20 March 2015 on a dive to 30.5 m.

General benthic features

Most of the 61% algal cover is sediment-laden turf (31%) and erect algae (20%), with gray carbonate films over pavement (e.g., Image 3).

3

Across 18 genera, Porites holds 24% of the coral and Acropora 23%, with Pocillopora third at 20%.

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Formal transects recorded 14% coral against 61% algae, but the composition of the ground is the story: coralline algae is almost absent at 2.9%, while turf-plus-sediment takes 31%, erect algae 20%, and bare substrate 15%.
• Transect mean 14 ± 1.5% SE (n = 13 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 14% (Mayfield & Dempsey 2026, Oceans, supplemental S1).
• The two depth strata carry near-identical cover, 13% and 14%, yet algae falls from 68% to 40% between them and the genus order inverts, Acropora leading the shallower and dropping to eighth in the deeper.
• 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 61% of the benthos.
• The transect figure is this site's authoritative cover value; no image-derived product overrides it.

Stressors

Published bleaching is 9.0%, and the photographs neither confirm nor dismiss it: one colony shows textbook white branch tips over pigmented bases, another is stark white but may be recent death, so bleached individuals were present in March, yet 9% of coral is far more than the frames show Image 1.

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The photographs show no disease lesion, predation, or crown-of-thorns. Anderson's sampling sheet logs both colonies sampled here as 5% pale or sickly (see Dive record below). The Living Oceans Foundation transects here recorded no cyanobacteria and no recently dead coral.

Fish and other fauna

The vertebrate fauna is the standout: two gray reef sharks, a hawksbill-type turtle, a massed acanthurid aggregation (e.g., Image 2).

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Comparisons with other data

Apart from the Living Oceans Foundation survey shown here, we found no other surveys at this site as of 2026. If you would like to share yours, please email us.

Dive record

Anderson sampled two pocilloporid colonies on this dive for a collaborator (species are field calls; the sampling sheet): Pocillopora sp. ChJo98 (collected 08:32 at 30.0 m; a large colony, 5% sickly or pale, healthy part sampled) and ChJo99 (08:43, 20.0 m; a large colony, likely P. verrucosa and very common at the site, 5% pale or sickly, pale part sampled). The dive notes record intense surge, no hard structure above 15 m, and sharks, lobsters, and turtles, and no P. damicornis, P. acuta, or Seriatopora at the site. 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

Aspect follows Anderson's field sheet (LOF fellowship 2016 workbook: 'lagoonal bank reef', 'leeward'); the expedition's 933-site table classes the station as 'intermediate' (bank reef). Esri World Imagery (no LOF habitat map covers the Great Chagos Bank) shows open water with no visible bottom at the pin, inside the Great Chagos Bank lagoon, so it cannot test the aspect; the sheet's lagoon position stands.