### BIPB65 — Peros Banhos
**CRD page:** [Peros Banhos Coral Surveys (Apr–May 2015)](https://coralreefdiagnostics.com/peros-banhos-)

**15 Apr 2015**
**GPS:** 5.41077°S, 71.80349°E
**Setting:** protected submerged lagoonal patch reef, 26 m
**Coral cover:** 41.4% (4 formal transects, D1–D4; **algal cover 31.4%**) · **published image bleaching:** 8.3%
**Live hard coral cover across methods:** formal transects 41.4% · CoralNet points 28.5% · Coralscapes masks 29.1% (32 frames). These products have different sampling footprints and denominators and should not be averaged.
**Temperature:** 30.5 °C · **Salinity:** 34.3
**Photo review:** all 35 frames examined — 2 at the folder top level plus 33 in the nested `BiPb65-CoralNet` subfolder (see Flag 2 on the real vs. multi-method frame count)
**Representative photos:** P4150620.jpg, P4150634.jpg, P4150592.jpg, P4150595.jpg, P4150626.jpg

BIPB65 is a moderately coral-dominated lagoonal patch reef at 26 m, with 41.4% formal coral cover against 31.4% algae and — notably — 15.6% crustose coralline algae, one of the higher CCA readings among the Chagos sites reviewed so far, plus 19.4% bare substrate. Twenty-three coral genera are recorded, but the assemblage is carried overwhelmingly by one: ***Acropora* holds 27.02% of the benthos, 65% of all the coral cover on the reef.** *Porites* is a distant second at 6.61% (16% of the coral), followed by *Pocillopora* 2.35% and *Montipora* 2.10%. Everything else — *Pavona*, *Platygyra*, *Stylophora*, *Goniastrea*, *Acanthastrea*, *Echinopora*, *Astreopora*, *Leptastrea*, *Psammocora*, *Cantharellus*, *Favia*, *Lobophyllia*, *Heliopora*, *Favites*, *Ctenella*, *Millepora*, *Montastrea*, *Cyphastrea* and *Leptoseris* — sits below 0.6% each and together contributes barely 2.5% of the coral present.

**The four depth transects tell a consistent-genus, variable-cover story rather than the genus handoffs seen at some other sites.** D2 carries the highest total cover at 55.78% (algae 28.18%), of which *Acropora* is 40.90% — 73% of the coral on that transect. D3 drops to the lowest cover on the reef, 28.47% (algae 31.2%), yet *Acropora* still holds 73% of what coral is there (20.73%). D1 has the highest algal cover by far — 51.7%, nearly double every other transect — with total coral at 37% and *Acropora*'s share of that coral falling to 60%, its lowest showing; *Porites* compensates somewhat, reaching 9.30% (25% of the coral, its best showing on the reef). D4 has the lowest algal cover, 14.67%, with coral at 44.47% and *Acropora* again down to 54% of the coral present; this is also the only transect where *Platygyra* (1.07%) and *Acanthastrea* (1.00%) register. Read together, *Acropora* dominance is highest where algae is moderate-to-low (D2, D3) and lowest where algae is either very high (D1) or very low (D4) — a pattern that does not map cleanly onto algal cover alone, and the site-level figures of 27.02% *Acropora* and 6.61% *Porites* describe no single transect precisely.

The photographs match this *Acropora*-first structure closely. P4150571, P4150604, P4150606, P4150613, P4150623, P4150630 and P4150631 all show extensive tabular and corymbose *Acropora* fields running across the reef flat and slope, tables stacked several deep in places with fusiliers and anthias working over them — the visual counterpart to the 55–73%-of-coral *Acropora* dominance recorded on D2 and D3. P4150620, P4150621, P4150624 and P4150633 show a denser, more mixed coral garden: massive lobate *Porites*-type colonies, brain-coral heads, encrusting purple coralline framework and digitate thickets crowded together — consistent with the higher *Porites* and lower *Acropora* share recorded at D1 and D4. P4150628 and P4150629 are close frames of a large dead or heavily bioeroded massive coral head riddled with holes, colonized by a vivid purple-blue encrusting sponge, pink CCA and a resident moray eel — a good match for the site's elevated 15.6% CCA reading. A pale gorgonian sea fan is visible in the background of P4150589 and P4150606; octocorals are not part of the scleractinian benthic dataset but their presence is worth noting.

**Condition at this site is mixed.** The published image-based bleaching figure is a moderate 8.3%, and most of the reef in the photographs reads as healthy tan-to-gold *Acropora* and *Porites* with normal pigmentation. But several frames show colony-scale pallor that reads as more conspicuous than that figure alone would suggest. P4150595 shows a large expanse of pale cream-white branching coral occupying the center of an otherwise tan-gold *Acropora* field. P4150626 shows a single stark white-cream corymbose colony sitting directly beside fully pigmented tan and green neighbors of the same growth form. P4150622 and P4150635 are macro pairs that make the contrast unambiguous: a white branching colony (consistent with *Acropora* or *Pocillopora*) growing immediately next to a vividly pigmented lime-green colony of similar form, tissue intact on both, no algal overgrowth — colony-scale bleaching, not a lighting artefact. These are scattered, localized colonies rather than a reef-wide whitening, and they are broadly consistent with — if visually more striking than — the published 8.3% mean. Fauna in the imagery include at least three frames of a whitetip reef shark (*Triaenodon obesus*) resting motionless on sand beneath coral overhangs (P4150592, P4150596, P4150597) and a moray eel in a bioeroded coral head (P4150628/629), both unremarkable but worth recording.

<b>Assemblage composition.</b> Formal transects give 41.4% coral and 31.4% algae across 23 genera, overwhelmingly carried by *Acropora* (65% of all coral present) with *Porites* a distant second; CCA at 15.6% and bare substrate at 19.4% are both comparatively high for the region. The photographs document extensive tabular/corymbose *Acropora* fields, a denser massive-coral-and-CCA zone matching the higher-*Porites* transects, scattered but unambiguous colony-scale bleaching, and resident whitetip sharks and a moray eel.

**Flags:**
1. **Extensive filename collision with BIPB63.** Fifteen frame numbers — P4150564, 603, 622–632, 634 and 635 — exist under identical filenames in both `BiPb63-great dive-finished/BiPb63-CoralNet` and `BiPb65-finished/BiPb65-CoralNet`, confirmed as genuinely different images by differing byte sizes (e.g. P4150564 is 2.92 MB at BIPB63 vs. 2.61 MB at BIPB65; P4150626 is 4.12 MB vs. 2.80 MB). Both sites were shot the same day (15 April 2015). **Any tool that keys on bare frame filename will mix these two sites — always carry the full folder path.**
2. **Frame-count mismatch, minor.** `chagos_multimethod_cover_by_site.csv` records `n_photos = 32` for the CoralNet/Coralscapes figures, but the folder holds 35 stills (2 top-level + 33 in `BiPb65-CoralNet`). The multi-method percentages rest on roughly 32 of the 35 available frames; not severe, but the two methods and the full photo review are not scoring identical image sets.
3. **Genus-code correction: CNEL = *Ctenella*, not *Cynarina*.** The `sitefacts.py` helper script's internal lookup table prints CNEL as "Cynarina," but the source benthic CSV (`BIPB65_benthic.csv`, the authoritative file) records CNEL as *Ctenella* (0.05% of benthos). This shard follows the CSV. The mislabeling appears to be a bug in the script's code table, not a data problem, but should be checked against other Chagos site shards that used the script's printed genus names uncritically.
4. **Photographic bleaching looks locally more pronounced than the 8.3% site figure alone conveys.** P4150595, P4150622, P4150626 and P4150635 show clear colony-scale white/cream branching corals directly beside fully pigmented neighbors of the same growth form. The site-level figure is taken as published; these frames are flagged as corroborating, more vivid evidence rather than a contradiction.
5. **Fauna of note:** a whitetip reef shark (*Triaenodon obesus*) resting under coral ledges appears in at least three frames (P4150592, P4150596, P4150597), and a moray eel occupies a bioeroded coral head in P4150628/629. Neither is a condition concern; both are recorded for completeness. A gorgonian sea fan is also visible in P4150589 and P4150606 — octocorals are not captured in the scleractinian-only benthic dataset.
6. **The published bleaching figure is a COMPUTER-VISION product, not an in-situ observation.** It comes from CoralNet annotation of the informal survey images (Mayfield & Dempsey 2026, *Oceans*). Per-image human-vs-model agreement is substantially weaker for bleaching than for cover: r = 0.40 for bleached against r = 0.72 for live hard coral (`CHAGOS_MULTIMETHOD_README.md`). Treat the site bleaching percentage as the weaker of the two published numbers, and never read it as a diver's field estimate.

**Benthic data:** [Download BIPB65 benthic survey data (CSV)](../benthic_data/BIPB65_benthic.csv) — scleractinian cover by genus with full names, plus substrate and algal categories, from the LOF BIOT-1 survey (Mayfield & Dempsey 2026, *Oceans*, supplemental file S1).