Chagos Archipelago - Great Chagos Bank West (BITB47)

Setting

BITB47 is a protected submerged patch reef inside the Three Brothers lagoon at 29 m, surveyed 24 March 2015, and it is one of the best reefs in this dataset: 53.7% coral against 35.5% algae, 20th of 109 Chagos sites for cover, and coral-abundant and genus-rich at once, with 29 genera, 19th of 109.

General benthic features

Only 6.6% of the benthos is bare substrate and 4.1% non-coral invertebrates. Acropora leads at 15.95% of the benthos and Porites at 12.73%, together 53% of all coral, and evenness is the highest of its group. The depth profile is the finding: cover climbs monotonically 48.2%, 55.1%, 57.9% while algae falls 43.8% to 24.4%, the middle stratum is the diversity peak carrying every one of the site's 29 genera, and leadership hands over at the bottom, where Porites jumps to 25.10% of the benthos, 43% of that stratum's coral and four times its mid-depth value, pushing Acropora into second. The blue coral Heliopora occurs at the middle stratum and nowhere else.

Coral cover

The image cover figures (CoralNet 30.0%, Coralscapes 25.7%) rest on those same two photographs and are illustrative only, never to be averaged with the transect value. Coral cover: 54%. 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 35.5% of the benthos. The transect figure is this site's authoritative cover value; no image-derived product overrides it. Across methods the same reef reads: transects 53.7% · CoralNet points 30% · Coralscapes masks 25.7% (2 frames). These products have different sampling footprints and denominators and should not be averaged.

Stressors

Bleaching is 5.56% on the site table's Mean(%bleaching) column, 65th of the 98 sites carrying a value, and both runs agree, so the canonical % bleaching (2nd training) figure is the same. Condition, though, cannot really be assessed: the camera housing fogged and the entire photographic record is two frames taken 64 seconds apart. They show a dense mixed high-cover mosaic and one large gold tabular Acropora carrying an older partial-mortality lesion already colonized by coralline algae; no bleaching field, crown-of-thorns, or disease is visible, but from two frames that is weak evidence (e.g., Image 1, Image 2).

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Comparisons with other data

No prior survey data from this site. If you would like to share yours, please email us.