### BIEA17 — Eagle Island
**CRD page:** [Eagle Island Coral Surveys (Mar 2015)](https://coralreefdiagnostics.com/eagle-island-201503)

**14 Mar 2015**
**GPS:** 6.18099°S, 71.34828°E
**Setting:** protected emergent fringing reef, inside the lagoon, 29 m
**Coral cover:** 4.8% (15 formal transects, D2–D4; **algal cover 59.7%**) · **published image bleaching:** the `Mean(%bleaching)` cell is blank for this site — no value exists, and none may be inferred
**Live hard coral cover across methods:** formal transects 4.8% · CoralNet points — none · Coralscapes masks — none. **No imagery exists for BIEA17, so neither computer-vision product was ever generated and no multi-method comparison is possible here.** Where those products do exist elsewhere in Chagos they carry different sampling footprints and denominators from the transects and should not be averaged with them; at this site the transect figure stands alone.
**Temperature:** 29.6 °C · **Salinity:** 34.0
**Photo review:** **none — no photographs exist for this site anywhere.** **Anderson dived here, but no imagery survives**: the published site table's `submitted to CoralNet?` column reads **"no photos"** and the supplement's `formal vs. informal comparison` sheet flags it the same way. No folder resolves to site number 17 under any prefix or casing; the site returns zero photo directories and zero frames. The CRD Eagle Island page records the dive and a taxonomic rather than photographic result — ***Pocillopora acuta*, *P. damicornis* and *Seriatopora* spp. were all noted as absent** (see Flag 4). **Everything below therefore rests on transect point counts alone, and reef condition at BIEA17 cannot be assessed** — bleaching, tissue loss, disease, predation scarring, COTS, fish and macrofauna are all simply *unavailable*, and must never be read as zero or inferred from neighbouring Eagle Island sites.

**BIEA17 is the poorest site at Eagle Island and third-poorest in the archipelago: 4.8% coral cover, 107th of 109**, against an island mean of 19.4% and a dataset mean of 37.9%. Its **algal cover of 59.7% ranks 7th of 109 — in the top decile** — for a coral-to-algae ratio of 0.08. Fifteen formal transects across three depth strata (3,500 points) give bare substrate 21.6% and non-coral invertebrates 13.9% alongside those figures. The raw fifteen-transect mean is 6.29% ± 8.57 SD over a **0.0–31.0% range: the standard deviation exceeds the mean**, so the site is severely patchy at transect scale. One outlier drives it — `BIEA17_d2_T1` reads 31.0% coral while eleven of the remaining fourteen transects sit below 5%, and two read exactly 0.0%. Algal cover is far steadier at 60.04% ± 15.40.

Even at 4.8% cover, transects still resolve **12 nonzero genera — 101st of 109 for genus count**. All values below are **percent of total benthos, not percent of coral**, and the 12 genus columns sum to 4.79%, matching the published cover figure. ***Porites* 2.29% (47.8% of live coral)**, ***Pocillopora* 1.06% (22.1%)**, ***Ctenella* 0.39%**, *Montipora* 0.32%, *Pavona* 0.22%, *Psammocora* 0.15%, *Favia* 0.10%, *Acropora* 0.07%, *Goniastrea* 0.07%, *Coscinaraea* 0.06%, *Favites* 0.06% and *Leptoseris* 0.01%. H′ = 1.64, Simpson = 0.71, evenness J′ = 0.66. **The *Acropora* figure is the one to notice: 0.07% of the benthos and 1.5% of live coral, on a protected lagoonal fringing reef where *Acropora* is normally a leading genus** — at BITB48 and BITB49, the other two lagoonal sites in this group, it is first or second. *Seriatopora* reads zero, consistent with the CRD page note, **but transects resolve to genus only and cannot confirm a species-level absence, so none is asserted here.**

**The algal breakdown is the real story of this site, and it is a single number.** Of 59.7% total algae, **sediment-laden turf (PTSTS) alone is 44.42% — the highest value of all 109 Chagos sites**, against a dataset mean of 7.37% and eleven points clear of the runner-up, BICC50 at 33.22%. The remainder: crustose coralline algae 7.61% (93rd of 109, low quartile), erect algae 4.23%, plain turf 1.86% (108th of 109, second-lowest in the archipelago), macroalgae 1.34% and cyanobacteria 0.22%. **Nearly half the benthos is turf bound with sediment.** That one figure explains the 4.8% coral cover far better than "high algal cover" does: this is a protected, emergent, inside-lagoon fringing reef where **sediment retention, not macroalgal overgrowth, dominates the substrate** — and CCA at 7.61%, roughly half the archipelago's typical value, is exactly what a smothered substrate should read. Across the transects, pavement averages 70.56%, sand 17.09%, rubble 5.23%, dead coral 0.80%, and **recently dead coral reads 0.00% on every one of the fifteen transects — the loss here is not recent.** With no imagery, that cannot be independently checked.

**The depth profile is a near-total collapse of coral over three strata, and the sediment signal peaks in the middle of it.** D2 averages 10.17% coral (7 transects), D3 3.70% (6 transects), D4 **0.50%** (2 transects) — **a twentyfold decline, with coral effectively disappearing below the shallowest stratum.** Genus count falls with it: 9 genera at D2, 9 at D3, only 4 at D4. The compositional handover is as sharp as the quantitative one. At D2 the assemblage is *Porites*-led (6.71% of benthos) with *Pocillopora* second (2.11%) and nothing else above 0.30%. **At D3 *Porites* collapses from 6.71% to 0.07% — a hundredfold drop — and *Ctenella* takes the lead at 1.17%**, with *Pocillopora* 0.97% and *Montipora* 0.57%. At D4 only four genera remain, none above 0.20%: *Montipora* 0.20%, *Pavona* 0.10%, *Pocillopora* 0.10%, *Porites* 0.10%. **Meanwhile sediment-laden turf peaks at D3, not at the bottom: 41.57% at D2, 57.70% at D3, 34.00% at D4 — and crustose coralline algae collapses at exactly the same stratum, from 10.57% at D2 to 1.67% at D3 before recovering to 10.60% at D4.** Bare substrate runs 23.11% / 12.17% / 29.50%. **D3 is where this reef is most thoroughly smothered**, and D4's slightly better algal readings come with essentially no coral at all.

<b>Assemblage composition.</b> Fifteen transects across three strata give 4.8% coral against 59.7% algae on 12 nonzero genera, led by *Porites* (2.29% of benthos, 47.8% of coral) and *Pocillopora* (1.06%, 22.1%), with *Acropora* at a near-absent 0.07%. Coral cover is 107th of 109 and algal cover 7th of 109, and the single explanatory figure is sediment-laden turf at 44.42% — the highest of all 109 Chagos sites. Coral falls twentyfold from D2 to D4 as *Porites* hands over to *Ctenella* and then to nothing, with the sediment-turf maximum and the CCA minimum both landing at D3. **There is no photographic record whatsoever, so none of this can be corroborated visually and no statement about the reef's condition — bleaching, mortality, disease, predation or fauna — is possible at BIEA17.** It and BIDI11 read as near mirror images and are worth keeping as a pair: BIDI11 carries 40% coral on four genera over a CCA-dominated, turf-free floor; BIEA17 carries 4.8% on twelve genera over a floor that is 44% sedimented turf. **Substrate condition, not coral abundance, separates them.**

**Flags:** (1) **NO PHOTOGRAPHS EXIST FOR THIS SITE, THOUGH ANDERSON DIVED IT.** Zero photo directories resolve to site number 17 under any prefix or casing; `submitted to CoralNet?` reads "no photos". There are consequently no CoralNet points, no Coralscapes masks, no multi-method comparison, and **no basis for any condition assessment** — bleaching, disease, predation, COTS and fauna are unavailable, not zero. **This one is a genuine loss rather than an undived site**, and is worth a check of any unindexed 14 Mar 2015 camera cards before it is written off. (2) **THE PUBLISHED `Mean(%bleaching)` CELL IS BLANK.** BIEA17 appears in `formal vs. informal comparison` only as a placeholder row keyed under `site code 2`, with no cover, bleaching or image count. **% bleached is unavailable and must not be computed from anything else.** Corpus-wide the published bleaching figure is a **computer-vision product** rather than an in-situ observation, with per-image human-vs-model agreement of r = 0.40 for bleached against r = 0.72 for live hard coral (`CHAGOS_MULTIMETHOD_README.md`) — but here there is no figure at all to caveat. (3) **⚠️ THE PLACEHOLDER ROW LISTS BIEA17's ISLAND AS "Danger Island" — WRONG.** BIEA17 is Eagle Island in every other source: the site sheet, the transect sheet, the per-site workbook and the CRD page. A one-cell supplement error; **recommend correcting.** (4) **The CRD page's absence claim for *Pocillopora acuta*, *P. damicornis* and *Seriatopora* spp. is consistent with the transects but not testable from them** — the LOF point counts resolve to genus only, and *Pocillopora* is present at 1.06% of the benthos, so no species-level absence can be confirmed. **Anderson's judgement needed** on whether to report it as a survey result. (5) **THE SITE MEAN HIDES A 60-FOLD TRANSECT RANGE** (0.0–31.0%, SD 8.57 > mean 6.29): 4.8% is an average of a single 31% patch and fourteen near-barren ones, not a uniform condition. (6) **D4 RESTS ON ONLY TWO TRANSECTS.** Site cover is the unweighted mean of the three stratum means — (10.17 + 3.70 + 0.50) / 3 = 4.79 — so **those two transects carry a full 33% of the headline number**, against seven at D2 and six at D3. The dramatic 0.50% deep-stratum figure is the thinnest-supported part of the depth profile. (7) **PTSTS = 44.42% IS A DATASET-WIDE EXTREME** — highest of all 109 sites, six times the dataset mean, and the single most load-bearing number in this description. **Confirm against the raw LOF datasheet before citing it externally.** (8) **POINT-COUNTS ARE MIXED AND UNWEIGHTED** — ten 100-point and five 500-point transects, 3,500 points total, pooled without effort weighting; this affects how the SD reads. (9) **Integrity checks pass:** the 12 genus columns sum to 4.79% against a published 4.7905%; the six algal categories sum to 59.69% against a published 59.6889%. Both reconcile within rounding. (10) **Depth is published as 29 m at site level but only as strata D2–D4 in the depth table — no per-stratum metre values exist**, so the twentyfold coral decline cannot be tied to an absolute depth range. (11) **Recently dead coral reads 0.00% on all fifteen transects** — an explicit zero from the point counts, but with no imagery it cannot be cross-checked, and it says nothing about bleaching, which is not measured at this site at all.

**Benthic data:** [Download BIEA17 benthic survey data (CSV)](../benthic_data/BIEA17_benthic.csv) — scleractinian cover by genus with full names, plus substrate and algal categories (bare substrate, CCA, turf, sediment-laden turf, macroalgae, erect algae, non-coral invertebrates), from the LOF BIOT-1 survey (Mayfield & Dempsey 2026, *Oceans*, supplemental file S1).