Chagos Archipelago - Great Chagos Bank West (BITB49)

Setting

BITB49 is an intermediate-exposure submerged lagoonal patch reef inside the Three Brothers lagoon at 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, 46th of 109, four more than its northern neighbor on 20% less coral, with no genus holding even 30% of the coral. Acropora leads at 7.60% of the benthos, then Porites 6.57% and Pocillopora 3.83%. The depth profile inverts the usual pattern and is the real finding: the deeper stratum carries more coral (30.2% against 23.4%), more genera (23 against 20), and far less sediment-laden turf (3.9% against 15.2%), while Acropora collapses from 11.96% of the benthos to 3.25%, Porites and Pocillopora both more than double, and Montastrea rises thirty-fold from a trace to third rank.

Coral cover

Thirteen formal transects recorded 26.8% coral against 40.6% algae — 83rd of 109 Chagos sites for cover, 55th for algae — with 18.8% bare substrate and 13.8% 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. Coral cover: 27%. Live hard coral measured on the in situ benthic transects of the LOF BIOT-1 expedition (Mayfield & Dempsey 2026, Oceans, supplemental S1), against algal cover of 40.6% of the benthos. The transect figure is this site's authoritative cover value; no image-derived product overrides it.

Stressors

The published Mean(%bleaching) cell is blank in both CoralNet training runs, 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.

Comparisons with other data

No prior survey data from this site. 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.