### BIEG02 — Egmont
**Date:** 2015-03-10
**GPS:** 6.66706°S, 71.39087°E · **In-situ temperature:** 28.9°C
**Frames reviewed:** 23 of 23 (100% of the site folder, `BiEg02-finished-great dive`)
**Coral cover:** 31.8% (formal transect surveys) · **3.6%** of coral bleached (CoralNet analysis of informal survey images; Mayfield & Dempsey 2026, Oceans)
**Live hard coral cover across methods** (n=23 photos): transect 31.8% · CoralNet points 17.8% · Coralscapes 15.2%. Deviation vs transect -16.6 to -14.0 pp. **Mean of 3: 21.6% ± 8.9.** (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 — *Acropora* (tabular, corymbose, staghorn and digitate forms all present and dominant), *Pocillopora*, *Porites* (massive domes and knobby encrusting), *Montipora*, *Echinopora*, *Favites*/*Dipsastraea*, *Astreopora*, *Pavona*; hydrocoral *Millepora*. All calls are growth-form-based from photographs and given as "compatible with" — no specimen was examined; the *Pavona* and *Millepora* calls are the least secure.
**Representative photos:** P3100266.jpg, P3100277.jpg, P3100287.jpg, P3100298.jpg, P3100299.jpg

BIEG02 is an exposed Egmont barrier-reef slope, and the full 23-frame pass shows it is **not** the uniformly good reef the earlier four-frame description implied — it is sharply zoned, and that zonation is the site's defining feature. The reef top and upper slope carry genuinely spectacular *Acropora* development: P3100266, P3100287, P3100296 and P3100297 are wall-to-wall lilac and fawn corymbose and tabular *Acropora* tables, overlapping edge to edge with almost no exposed substrate, and P3100283 and P3100288 show extensive open-branched staghorn (*A. muricata*-type) thickets running downslope. Set among the acroporid tables are domal and knobby *Porites*, small purple-brown *Pocillopora* clusters, tan encrusting-to-laminar plates compatible with *Montipora*, and — in P3100281 — a distinctive dark ridged foliose colony compatible with *Echinopora* alongside polygonal-corallite faviid domes compatible with *Favites* or *Dipsastraea*. But an equally large share of the dive (P3100255, P3100256, P3100282, P3100299, and the deeper slope in P3100278 and P3100280) crosses low-relief pavement and rubble where turf-covered hardground carries only scattered small *Porites* mounds and isolated colonies, with coral cover well under 10% by eye. The site's 31.8% transect figure and the 15–18% photo-method figures are best read as an average across these two very different states, not as a description of either one. A close macro frame (P3100268) records the fine-scale texture the wide shots miss: magenta crustose coralline algae, boring-bivalve apertures, small pale *Acropora* recruits and encrusting sponge packed into a few centimetres of pavement.

Thermally this is an early-March dive, before the 2015 bleaching had properly developed, and the imagery matches the very low 3.6% site figure — but it is not zero, and the bleaching present is instructive. **P3100286 is the key frame**: four to five fully bone-white branching *Acropora* colonies stand out against pigmented neighbours in a single macro field, alongside several partially blanched colonies — a tight cluster of affected colonies rather than diffuse whitening. **P3100288** adds a second, different signal: a large massive *Porites* whose surface is chalk-white and algal-fuzzed across its entire upper face, sitting in the middle of a healthy staghorn thicket. That reads as recent mortality rather than active bleaching — a dead skeleton beginning to be colonised — and should not be pooled with the branching bleaching in P3100286. Elsewhere the reef is fully pigmented fawn, lilac and olive throughout.

The fauna is where this dive earns its "great dive" folder tag, and it includes two findings that matter. **A crown-of-thorns starfish is unambiguously present in P3100277** — a full-frame *Acanthaster* with long grey-green spines over a maroon disc, photographed alongside a stainless steel bone-rongeur laid on the substrate beside it, plainly a deliberate documentation or collection shot. This confirms the Coralscapes model's probable-COTS flag on this frame (17.7% of frame area) as a true positive. Separately, **two pincushion sea stars compatible with *Culcita novaeguineae*** appear — the brown black-netted cushion in P3100247 and a second, very cleanly photographed individual in P3100298, the latter resting within centimetres of a small white-tipped *Acropora*. *Culcita* is itself a corallivore, so with the *Acanthaster* this dive documents two coral-predator taxa at one site. Two grey reef sharks compatible with *Carcharhinus amblyrhynchos* patrol the blue water off the drop in P3100269 and P3100270. Dense silver schools — bigeye scad or fusiliers compatible with *Selar* or *Caesio* — sweep the reef top in P3100252, unicornfish compatible with *Naso* hang over the slope in P3100256, orange anthias compatible with *Pseudanthias* cloud every coral-dominated frame, and two palette surgeonfish compatible with *Paracanthurus hepatus* are clearly visible in P3100282. Survey gear appears in three frames (a transect T-bar, camera rig and yellow mesh collecting bag in P3100246; the bag again in P3100252; the rongeur in P3100277), fixing these as working survey images rather than pure scenics.

<b>Assemblage composition.</b> Across 23 analysed frames the Coralscapes masks put live hard coral at 15.2% of image area, of which <i>Acropora</i> (non-tabular) is the largest component at 62.6%; the rest breaks down as massive and meandroid 18.5%, other hard coral 9.3% of live cover. The independent 30-point human annotation of the same frames (690 points) gives live hard coral as 17.8% of all points and apportions it <i>Acropora</i> 61.8%, <i>Porites</i> 22%, other hard coral 8.9%, <i>Pocillopora</i> 7.3% of live coral. Non-coral cover is dominated by crustose coralline algae 4.2%, turf 29.7%, <i>Halimeda</i> 2.5% of all points. Structural loss registers as dead coral 2.7% of image area and rubble 6.8%. Bleaching stands at 0.4% of annotated points, concentrated in <i>Acropora</i> 0.3%, other hard coral 0.1% of points. Conspicuous fauna and sessile invertebrates appear as sponges in 7 frames, urchins in 1 frame, sea cucumbers in 1 frame. <b>Crown-of-thorns detected</b> in P3100277.jpg (17.7% of frame) — see the COTS log. The very high turf figure (29.7% of points) is consistent with the extensive low-relief pavement zone described above, and is the strongest quantitative support for treating this site as two habitats averaged together.

**Flags:** (1) **CONFIRMED COTS in P3100277** — the model flag is a true positive; a rongeur beside it indicates deliberate documentation or removal. Escalated to the COTS log. (2) **Two corrections to the previous description, both from frames it never opened:** the "white feather-duster worm colony beside the measuring calipers" in P3100277 *is the crown-of-thorns starfish and a surgical rongeur* — that sentence should not be reused anywhere; and the cushion star in P3100298 is a *Culcita*-type pincushion star, **not** a *Protoreaster* chocolate-chip star (a genuine *Protoreaster* does occur at BIBL82 — do not merge the two records). (3) The previous claim that "cover was uniformly good throughout" is contradicted by roughly half the frames; the site is strongly zoned. (4) P3100288's white massive *Porites* is read here as recent mortality rather than active bleaching — cause unresolved from imagery alone. (5) The dark elongate object on the substrate at lower left of P3100281 has an artificial-looking straight profile; it may be a dead coral branch or debris, unresolved at this resolution. (6) Depth is not recorded per frame; the two-habitat structure is inferred from framing and light, not instrument data.

**Benthic data:** [Download BIEG02 benthic survey data (CSV)](../benthic_data/BIEG02_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).