Chagos Archipelago - Peros Banhos (BIPB76)

Setting

BIPB76 is a windward fore reef slope outside Peros Banhos (dived to 21.3 m), surveyed 19 April 2015, and two numbers, given under Coral cover, define it: its coralline algae and its fleshy turf.

General benthic features

Across 18 genera, Porites holds 37% of the coral and Acropora 31%. Down the profile cover falls by more than half, 55% to 32% to 21%, and Acropora vanishes as it goes — 28% of the benthos at the shallowest stratum, 2.6% at the next, zero at the deepest, where only four genera are recorded at all. The photographs explain both patterns: below the antipatharian-studded upper slope lies an extensive field of large, intact but dead tabular Acropora plates, coated in turf-and-sediment film rather than coralline crust (e.g., Image 2, Image 4).

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Coral cover

• Reference: Mayfield & Dempsey (2026)
• CoralNet submission package
• Formal transects recorded 40% coral against 34% algae, but coralline algae is only 3.2% of the benthos, while fleshy turf is 23%, with bare substrate at 11% and non-coral invertebrates at 15%.
• Transect mean 40 ± 5.0% SE (n = 10 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 36% (Mayfield & Dempsey 2026, Oceans, supplemental S1).
• 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 34% of the benthos.
• Image-based estimates (CoralNet, DINOv3, CoralSCOP, and Claude) are listed in the method table for comparison only; the transect figure is this site's cover value.

Stressors

Published bleaching is 22% — and at least seven frames carry bone-white tables and branching colonies beside fully pigmented neighbors, so the imagery confirms rather than merely permits the figure (e.g., Image 3).

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One encrusting colony with a white band running into dead algal surface could not be resolved between tissue loss and bleaching followed by mortality. No crown-of-thorns was seen and no diagnostic disease sign was resolved in the photographs, but Anderson's sampling sheet records two of the three colonies sampled here as bleached or diseased (possible disease). Anderson's sampling sheet records three pocilloporid colonies sampled here for a collaborator (species by field call): Pocillopora verrucosa ChJo194 (21.0 m, large, healthy) and ChJo195 (14.8 m, 50% sickly (bleached or diseased)); Pocillopora sp. ChJo196 (10.9 m, 60% diseased or bleached). Pocillopora acuta colonies from this archipelago were analyzed in Thomas et al. (2026, Global Ecology and Biogeography 35:e70305, https://doi.org/10.1111/geb.70305). The Living Oceans Foundation transects here recorded no cyanobacteria and 1.1% recently dead coral.

Comparisons with other data

The XL Catlin Seaview Survey covered a nearby station (transect 36011) in 2015, 0.16 km from the pin; we could not confirm that it is the same reef. Within 5 km, two XL Catlin Seaview Survey stations recorded station-year means of 21–26% hard coral cover in 2015; the nearest, XL Catlin Seaview Survey at transect 36011, 0.16 km away, read 21% in 2015.

Other notes

Reef type and aspect follow the LOF habitat map: the pin lies 17 m from 'deep fore reef slope' and 'shallow fore reef slope' on the atoll's east rim, which faces east-northeast, windward of the southeast trades. Anderson's field sheet (LOF fellowship 2016 workbook) records 'fringing reef', 'windward'; the expedition's 933-site table classes the station as 'exposed' (fringing reef).