### BIEG05 — Egmont
**Date:** 2015-03-11
**GPS:** 6.64248°S, 71.31116°E · **In-situ temperature:** 29.0°C
**Frames reviewed:** 66 of 66 (100% of the site folder, `BiEg05-great dive` — the third-largest photo set in the Chagos collection)
**Coral cover:** 46.7% (formal transect surveys) · **6.5%** of coral bleached (CoralNet analysis of informal survey images; Mayfield & Dempsey 2026, Oceans)
**Live hard coral cover across methods** (n=66 photos): transect 46.7% · CoralNet points 32.9% · Coralscapes 32.2%. Deviation vs transect -14.5 to -13.8 pp. **Mean of 3: 37.3% ± 8.2.** (SD here reflects systematic method bias, not precision — photo methods read low at high cover; see CHAGOS_MULTIMETHOD_README.md.)  
**Coral genera identified:** 8 scleractinian + 1 hydrocoral + 2 octocoral — *Acropora* (tabular overwhelmingly dominant, plus corymbose, staghorn and digitate), *Pocillopora*, *Porites* (massive domes and digitate), *Montipora* (foliose and encrusting), *Platygyra*, *Favites*/*Goniastrea*, *Astreopora*, *Echinopora*/*Turbinaria*; hydrocoral *Millepora*; octocorals — large sea fans compatible with *Annella* or *Subergorgia*, and leathers compatible with *Sarcophyton*. Also present: giant clam compatible with *Tridacna* and wire coral compatible with *Cirrhipathes*. Growth-form calls from photographs, given as "compatible with".
**Representative photos:** P3110483.jpg, P3110481.jpg, P3110480.jpg, P3110434.jpg, P3110390.jpg

BIEG05 is the best reef of the Egmont series and the 46.7% transect figure — the highest yet reviewed — is fully earned. The defining structure is a **tabular *Acropora* plain**: across P3110434, P3110439, P3110440, P3110442, P3110443, P3110448, P3110454, P3110459, P3110478 and P3110485 the reef is carpeted in overlapping golden tables, some stacked plate-on-plate in tiers, running unbroken to the limit of visibility. P3110434 and P3110415 isolate single perfect *A. cytherea*/*hyacinthus*-type tables with clean white growth margins, and P3110480 records a startling lime-green corymbose colony — a natural fluorescent-pigment morph — beside a Moorish idol. But the site is more than one habitat. The dive also crosses a **deep wall or steep drop** (P3110390, P3110404, P3110414, P3110415, P3110417) where the tabular corals give out and the community switches to large sea fans compatible with *Annella* or *Subergorgia*, big ridged massive *Porites* boulders, red and magenta encrusting sponge, wire corals compatible with *Cirrhipathes*, bannerfish compatible with *Heniochus*, and red soldierfish. A third facies — mixed low-relief pavement with domal *Porites*, digitate *Acropora* and meandroid *Platygyra* — fills P3110403, P3110466, P3110467, P3110477 and P3110479. Fine-scale diversity comes from the macro frames: P3110420 is an unambiguous branched *Millepora*, P3110469 packs domal *Porites*, yellow meandroid *Platygyra*, digitate *Acropora* and encrusting colonies into one crowded field, and P3110412 resolves honeycomb-corallite *Favites*/*Goniastrea* over CCA-crusted pavement.

**Bleaching at BIEG05 is the clearest photographic record in the reviewed set, and it is more informative than the 6.5% site figure alone conveys.** Three frames carry it. **P3110481 is the single most valuable bleaching image found so far** — a full-frame macro of one large tabular *Acropora* in which broad patches of bone-white branches are interleaved with fully pigmented brown branches on the same colony, an unmistakable record of *partial-colony* bleaching caught mid-progression. **P3110438** shows a completely bleached *Pocillopora*, stark white against pigmented *Porites*, faviids and *Montipora* neighbours. **P3110458, P3110460 and P3110461** add a subtler and arguably more important signal: broad areas of tabular *Acropora* whose surfaces are pale grey-white and dulled with algal film rather than bright bleach-white, which reads as recent post-bleaching mortality rather than active bleaching. P3110449 shows the end state — a branching colony now dead and overgrown by crustose coralline algae. Read together, on a single 11 March dive this site documents the entire sequence: healthy → partially bleached → wholly bleached → freshly dead → CCA-overgrown. That is a genuinely useful record given Anderson's interest in partial-colony bleaching from photographs, and it sits at the top of the archipelago's cover range, so the loss was from a high starting point.

**The site also carries the most complete photographic record of the survey methodology anywhere in the Chagos set — five frames.** P3110482 and P3110483 show a diver in yellow fins handling a large white PVC quadrat frame, with P3110483 catching the frame laid directly on a tabular *Acropora* table. P3110484 puts the diver and quadrat in the middle distance while blue fusiliers compatible with *Caesio* or *Pterocaesio* stream past. P3110470 and P3110472 catch the quadrat frame drifting at frame edge mid-deployment. P3110441 and P3110451 show the transect line itself running across the substrate. These images tie this site's 46.7% number to the physical act that produced it, and are the obvious candidates for any methods figure.

Faunally the site is diverse and, in one respect, distinctive: **BIEG05 is the emperor/bream site**. Schools of large silvery *Monotaxis*- or *Gnathodentex*-type emperors dominate P3110455, P3110456, P3110457, P3110462, P3110463 and P3110464, sometimes twenty or more in frame, a fish community structure not seen at BIEG02–04. Parrotfishes compatible with *Scarus* or *Chlorurus* — red-brown with green-yellow tails — work the reef in P3110471, P3110474, P3110475 and P3110477. A **silvertip shark (*Carcharhinus albimarginatus*-type)** patrols the drop in P3110388, a **bluefin trevally (*Caranx melampygus*)** hunts in P3110425, and jack schools cross the blue in P3110479. Two frames (P3110413 and P3110422) hold an **octopus**, mantle and eye clearly visible, wedged in rubble beside a *Pocillopora* — with a third possible sighting in P3110412. A large **giant clam compatible with *Tridacna*** with fluted scaly shell and visible mantle occupies P3110435. Reef fish include a **regal angelfish (*Pygoplites diacanthus*)** in P3110465 and P3110476, powder-blue surgeonfish (*Acanthurus leucosternon*), Moorish idols, soldierfish compatible with *Myripristis*, and a large spotted grouper compatible with *Plectropomus* in P3110466 and P3110467.

<b>Assemblage composition.</b> The Coralscapes and CoralNet figures are given in the cover line above. At 32.9% and 32.2% the two photo methods agree almost exactly, and both sit ~14 pp below the transect — the same systematic offset seen at every Egmont site, and again best explained by sampling frame rather than model error. Notably, BIEG05 is the one site where the visual impression *supports* the high transect number: the tabular plain in P3110439/P3110442/P3110478 is as close to continuous coral cover as anything in the Chagos set.

**Flags:** (1) **P3110481 is a partial-colony bleaching record of unusual quality** — white and pigmented branches on one table — and should be pulled out for the partial-bleaching-from-photos analysis. (2) **P3110458/P3110460/P3110461 are read as recent post-bleaching mortality, not active bleaching** (dull grey-white with algal film, not bright white); logged separately so the two are not pooled. (3) The small round white spots scattered across table surfaces in P3110460 are **unresolved** — possible early bleaching foci, predation scars, or settled organisms; they should not be scored either way without closer inspection. (4) Five methodology frames identified (P3110470, P3110472, P3110482, P3110483, P3110484) plus two transect-line frames (P3110441, P3110451). (5) The octopus appears in P3110413 and P3110422, with P3110412 a probable third; whether these are one animal revisited or separate individuals cannot be determined. (6) The emperor/bream schools are left at genus-pair level (*Monotaxis*/*Gnathodentex*) — the diagnostic head markings are not resolvable in these frames. (7) The dark foliose plates in P3110485 could be *Acropora* tables or foliose *Montipora*/*Echinopora*; the light is too poor to separate them. (8) No per-frame depth data; the wall/plain/pavement zonation is inferred from framing, light and blue-water backdrop.

**Benthic data:** [Download BIEG05 benthic survey data (CSV)](../benthic_data/BIEG05_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).