### BIPB61 — Peros Banhos
**CRD page:** [Peros Banhos Coral Surveys (Apr–May 2015)](https://coralreefdiagnostics.com/peros-banhos-)

**14 Apr 2015**
**GPS:** 5.39123°S, 71.74974°E
**Setting:** windward/intermediate-exposure emergent channel forereef, 30 m
**Coral cover:** 20.0% (3 formal transects, D2–D4; **algal cover 50.0%**) · **published image bleaching:** 12.9%
**Live hard coral cover across methods:** formal transects 20.0% · CoralNet points 20.0% · Coralscapes masks 13.1% (20 frames). These products have different sampling footprints and denominators and should not be averaged.
**Temperature:** 29.9 °C · **Salinity:** 34.5
**Photo review:** all 24 stills examined — 9 in the top-level folder, 15 in the `BiPb61-CoralNet` subfolder (see Flag 1)
**Representative photos:** P4140639.jpg, P4140633.jpg, P4140672.jpg, P4140654.jpg, P4140637.jpg

BIPB61 is a low-cover, algal-dominated channel forereef on the windward rim of Peros Banhos, and the numbers that distinguish it are not the coral ones. At **20.0% transect coral cover it ranks 94th of the 109 Chagos sites** — the 16th lowest in the archipelago — against **50.0% algal cover**. The single most unusual figure is turf: **22.3% of the benthos, the second-highest turf value in the entire 109-site set** (only BIBL86, at 22.6%, exceeds it). Non-coral invertebrates take another **22.4%, ranking 13th of 109**. Crustose coralline algae hold 15.4%, bare substrate 7.6%, turf-with-sediment 6.3%, erect algae 4.3% and macroalgae 1.7%. This is a reef whose surface is largely turf, sessile invertebrates and coralline pavement, with coral as the minority occupant.

The coral that is present is a *Porites* assemblage with a thin tail. ***Porites* alone holds 8.99% of the benthos — 45% of all coral recorded** — followed by *Acropora* 4.54%, *Pocillopora* 2.44% and *Montipora* 1.59%. Below that the list falls away fast: *Leptastrea* 0.54%, *Astreopora* 0.38%, *Favites* 0.31%, *Pavona* 0.29%, *Favia* 0.23%, *Montastrea* 0.20%, *Gardineroseris* 0.11%, *Symphyllia* 0.10%, then *Acanthastrea* and *Millepora* at 0.07%, *Goniastrea* at 0.04%, and a seven-genus floor at 0.017% each — *Coscinaraea*, *Fungia*, *Galaxea*, *Heliopora*, *Oxypora*, *Scolymia* and *Stylophora*. Twenty-two genera are non-zero, but sixteen of them together account for under 2.5% of the benthos.

**The depth pattern is a shallow-to-deep genus handover, and the middle band is the poorest.** D2 carries 24.2% coral and is the only band *Acropora* leads — 8.00% against *Porites*' 7.40%, with *Pocillopora* unusually strong at 4.80%. D3 drops to **15.2%, the site's minimum**, and the order inverts hard: *Porites* 8.97% against *Acropora* 2.57%. D4 recovers to 20.7% with *Porites* at its site maximum of 10.60% and *Acropora* at 3.05%. Genus richness runs the other way from cover — 9 genera at D2, 11 at D3, **18 at D4** — so the deepest band is the poorest in *Acropora* and the most genus-diverse. Algal cover is high in all three bands (50.4%, 52.6%, 47.0%) and barely varies, which is the clearest signal that the algal dominance here is a site property rather than a depth effect.

The photographs match that description closely, and they explain the invertebrate figure that the transect list cannot. **Gorgonian sea fans are the most conspicuous non-scleractinian element of this reef.** P4140654 is the defining frame: a slope falling into blue water carrying a dense stand of large yellow-green gorgonians and whip corals, with a haze of small planktivores above and only pale, sparsely colonised pavement beneath. P4140635 and P4140640 show the same fans and dark whip corals along the slope, P4140641 catches them beside a deployed transect tape with a diver working above, and P4140633 places them across a broad, low-relief mixed bottom of small massive domes, digitate colonies, foliose plates and black finger sponges. **None of these octocorals appear anywhere in the transect data**, which records only scleractinians plus *Millepora* and *Heliopora* — so the 22.4% non-coral invertebrate figure is the only place they are counted, and their contribution is not resolved to taxon.

Where coral does concentrate, it is *Acropora* in the shallows. P4140639 and P4140638 show near-continuous corymbose and tabular *Acropora* thickets working with sergeant majors, black triggerfish, humbug damsels and dense orange anthias — the photographic match to the 8.00%-*Acropora* D2 transect. Away from those patches the ground is exactly what the cover figure implies: P4140632 and P4140634 show wide pale pavement and rubble carrying widely spaced small massive domes and ruffled foliose colonies, and P4140636 shows the same at depth with a scrawled filefish over largely bare substrate. P4140637 is the best single frame for genus variety — a large massive *Porites* dome, encrusting and foliose plates, a clearly meandroid brain coral, small branching *Acropora*, orange sponges, red encrusting algae and a pink sea whip in one downward view.

**Bleaching is real here and is documented photographically.** The published image-based figure is **12.9%, which ranks 16th of the 98 Chagos sites carrying a bleaching value** — high for this archipelago. **P4140672 is unambiguous**: a top-down frame of a single large, entirely white massive colony, its lobed surface fully pigment-free, sitting on dark turf-covered pavement among small unbleached colonies. P4140651 holds a white digitate colony on the pavement beside a pale cream soft coral, and P4140640 and P4140632 each contain broad pale-to-white massive and plating colonies on the slope. These are consistent with a site-level figure in the low teens and were not used to compute it.

The site's other habitat is cryptic. P4140649, P4140650 and P4140653 are a sequence under a ledge or overhang holding a large aggregation of golden sweepers, with the ceiling carrying red and maroon encrusting algae and sponges, yellow encrusting sponges, ascidians and green *Halimeda*; orange anthias, a reddish soldierfish or bigeye and several larger silvery fish share the shelter. P4140648 covers the same habitat with a yellow-green whip coral and a scarred massive *Porites* dome on the sand at the overhang mouth. P4140651 adds a large emperor or snapper at close range. None of these frames carry usable benthic cover, but together they document the sponge-and-ascidian load that the 22.4% invertebrate figure records.

<b>Assemblage composition.</b> Formal surveys give 20.0% coral, 50.0% algae and 22.4% non-coral invertebrates, the coral 45% *Porites* and led by *Acropora* only in the shallowest band. The photographs contribute what the transects cannot: a substantial gorgonian and whip-coral stand, a sponge- and ascidian-dominated cryptic habitat, dense *Acropora* patches that are real but local, and at least one fully bleached massive colony.

**Flags:** (0) **GENUS CODE — SCOL, not SCOE.** This site records `SCOL` = *Scolymia* at 0.0167% of benthos; its `SCOE` cell is empty. `SCOE` and `SCOL` are separate columns in the LOF site table with disjoint site sets (8 sites carry SCOE, 5 carry SCOL, none both), so they are two different genera and *Scolymia* is what the data say here. Recorded for completeness: *Scolymia* is an Atlantic/Caribbean genus and is not expected in the Indo-Pacific, so the CODE may be mislabelled at source — but that is a question for the raw datasheet, not something to silently overwrite. (Contrast BIBL87 and BINI80, which carry SCOE = *Stylocoeniella*, an Indo-Pacific genus.)  (1) **This site's photographs are split across two folders and the benthic frames are in the subfolder.** The top-level `BiPb61-MANTA! finished` folder holds nine stills that are almost entirely *not* benthic — P4140628 is an Odyssey PAR logger in a "CAMPO LIBRE" housing (barcode DSL+86457) held at the surface beside the vessel, P4140629 and P4140630 are the manta-tow board on its towline, P4140661–663 are reef manta rays photographed with a diver and camera rig in frame, and P4140649/650/653 are the sweeper overhang. The 15 frames that actually show benthos are in `BiPb61-CoralNet`. **Any pass that reads only the top-level folder will conclude this site is photographically undocumented, which is wrong.** (2) **Frame-count mismatch:** the folders hold 24 stills (plus two .MOV files, P4140659 and P4140665), but `chagos_multimethod_cover_by_site.csv` records `n_photos = 20` for this site. The CoralNet and Coralscapes percentages therefore rest on a smaller set than "24 frames" implies; do not present a frame count beside those figures without saying which set it refers to. (3) **Gorgonians and whip corals are the visual signature of this reef and are absent from the transect genus list.** They are counted only inside the 22.4% non-coral invertebrate total, unresolved to taxon — the octocoral component of BIPB61 is unquantified. (4) **Turf at 22.3% is the second-highest value in the 109-site set.** This is the site's most distinctive number and is worth confirming against another method before publication. (5) **The 12.9% bleaching rank (16 of 98) is computed from the published `Mean(%bleaching)` column, which is known to carry at least one bad value** — BITB58 appears there as 22.22% when the corrected figure is 0.77%. The rank is therefore approximate; the underlying 12.9% for this site is taken as published. (6) The two video files were not reviewed. (7) **NON-CANONICAL BLEACHING RANK — added 2026-08-26.** Any "of 98" bleaching rank above was computed off the site table's `Mean(%bleaching)` column, which equals the **1st** CoralNet training run. Anderson's decision of 2026-08-26 (HOW_TO rule 4e) makes **`% bleaching (2nd training)` canonical**, The file carries TWO pools for it, and they are not interchangeable: a **110-row pool** ranking every dive (revisit dives included, so BIPB70B/72B/69C compete) and a **99-site pool** ranking one value per site. The rank quoted below is on the 110-row dive pool. For this site the canonical value is **12.00%, rank 29 of 110** (1st training: 12.00%, rank 24 of 110). The two runs agree to <0.05 pp on 100 of 110 rows and diverge only on the bleaching-onset dives, so for most sites the distinction changes the rank but not the number.

**Benthic data:** [Download BIPB61 benthic survey data (CSV)](../benthic_data/BIPB61_benthic.csv) — scleractinian cover by genus with full names, plus substrate and algal categories (bare substrate, CCA, turf, macroalgae, invertebrates), from the LOF BIOT-1 survey (Mayfield & Dempsey 2026, *Oceans*, supplemental file S1).