Chagos Archipelago - Great Chagos Bank North (BINI80)

Setting

BINI80 is a protected submerged bank reef on the north of the Great Chagos Bank, filed to Nelson Island, dived twice on 21 April 2015; the published site-depth cell is blank, so the reef has no absolute depth on record.

General benthic features

The assemblage is overwhelmingly monogeneric: across 20 genera, Acropora alone is 32.2% of the benthos, 75% of every coral on the site (e.g., Image 2, Image 3).

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Unusually there is no genus handover with depth — Acropora leads every station, 79%, 77%, and 62% of transect coral — while absolute cover halves, from 53.0% shallow to 24.0% deep.

Coral cover

Formal transects recorded 42.8% coral against 39.5% algae — 41st of 109 Chagos sites for cover — with fleshy turf at 19.4% of the benthos, 7th-highest of 109, only 8.4% coralline algae and 16.4% bare substrate (e.g., Image 1).

1

No CoralNet or Coralscapes product exists for this site, so the transect figure is its only cover number. Coral cover: 43%. 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 39.5% of the benthos. The transect figure is this site's authoritative cover value; no image-derived product overrides it.

Stressors

Crown-of-thorns predation is the finding, and it is unambiguous: at least eleven sightings across five frames in one day, including an aggregation of six or more animals on freshly exposed white skeleton and one starfish sitting exactly on the boundary between living plate tissue and fresh kill, on a reef three-quarters composed of their preferred prey (e.g., Image 4).

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The published bleaching cell is blank, one of 11 of 109 Chagos sites with no value in either CoralNet run, and no substitute was computed — which here is just as well, since white Acropora on a reef with active feeding fronts cannot be told from bleached tissue in a single still.

Fish and other fauna

Whitetip reef sharks appear on both dives.

Comparisons with other data

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