Chagos Archipelago - Great Chagos Bank West (BITB49)

Setting

BITB49 is an intermediate-exposure submerged lagoonal patch reef inside the Three Brothers lagoon (station CTD cast to 25 m), about 5 km south of BITB48, surveyed 24 March 2015 by the Living Oceans Foundation team; Anderson did not dive it.

General benthic features

Its strength is breadth rather than abundance: 26 genera, with no genus holding even 40% of the coral. Acropora leads at 9.3% of the benthos, then Porites 5.7% and Pocillopora 3.2%. The depth profile is the real finding: the deeper stratum carries more coral (30% against 23%), more genera (23 against 20), and far less sediment-laden turf (3.9% against 15%), while Acropora collapses from 12% of the benthos to 3.3%, Porites and Pocillopora both more than double, and Montastrea rises thirty-fold from a trace to third place.

Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Thirteen formal transects recorded 26% coral against 42% algae, with 17% bare substrate and 15% non-coral invertebrates, and individual transects ranging 10% to 46%, so the site figure averages very unequal ground.
• That deeper stratum rests on only four transects, so read it as indicative.
• The transect figure is its only cover number.
• 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 42% of the benthos.
• The transect figure is this site's authoritative cover value; no image-derived product overrides it.
• Transect mean 26 ± 3.0% 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 27% (Mayfield & Dempsey 2026, Oceans, supplemental S1).

Stressors

No mean bleaching value was published for this site in either CoralNet training run, so the site contributes nothing to any archipelago bleaching statistic. Recently dead coral reads exactly zero on every transect, with no imagery to check it against. The Living Oceans Foundation transects here recorded 0.2% cyanobacteria.

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.

Other notes

Condition cannot be assessed: no photographs exist for this site anywhere, so there are no CoralNet or Coralscapes products, no multi-method comparison, and no observation of bleaching, disease, predation, crown-of-thorns, or fauna — unavailable, not zero.