Chagos Archipelago - Speakers Bank (BISP89)

Setting

BISP89 is a deep, protected lagoonal patch reef inside Speaker's Bank, surveyed 24 April 2015 at 30.8 m.

General benthic features

Twenty-nine coral genera were recorded, and the three depth transects hand the lead over twice: Acropora holds 54% of the coral at the shallowest station, Stylophora leads at mid-depth, and Porites leads at the deepest, where cover peaks and algal cover falls away. The photographs show coral-abundant branching patches (e.g., Image 2) alternating with open plate-and-rubble pavement (e.g., Image 3) and conspicuous mixed fish schools (e.g., Image 4); some colonies looked pale but no frame justified a site-specific bleaching record, and no crown-of-thorns or disease signs were seen in the 13 stills reviewed.

234

Coral cover

Formal transects recorded 33% coral cover against 54.6% algae — 68th of 109 Chagos sites for coral but 14th for algal cover, on ground carrying the 9th-highest fleshy turf value in the archipelago. The bleaching percentage is a computer vision figure — CoralNet annotation of the informal survey images, not a diver's field estimate — and human-vs-model agreement is weaker for bleaching (r = 0.40) than for coral cover (r = 0.72). Image-based methods read this reef 24–25 points lower than the transects (CoralNet 8.3%, Coralscapes 8.9%); the three are not interchangeable and should not be averaged (see the full report).

Stressors

The published image-based bleaching figure is 9.2%.

Comparisons with other data

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