Coral Reef Diagnostics

Egypt Red Sea - Marsa Nakari-North (Marsa Nakari)

Reef Check Foundation
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Part of the regional summaries: Egypt and Red Sea

05
Coral Health Index: TBD
Photo: Anderson Mayfield/Coral Reef Diagnostics
Country
Egypt
Survey date(s)
2024-09-20
Coordinates
24.9305, 34.9622
Coral cover
23%
Manual point count (195 photos) · other methods below
Observations
bleaching
Heat stress
Today’s heat load
30.6°C13.2°C-weeks
16 Sep 2026 · Alert Level 2
5-year thermal stress load
5-year mean max. degree heating weeks (DHW)
15.6°C-weeksi
2021–2025
NOAA Coral Reef Watch — Egypt virtual station
i 5-year mean max. DHW is the mean of the annual maximum DHWs over the five complete years named above, not conditions today.
More infoEgypt (NOAA CRW virtual station) · Northern and Central Red Sea ecoregion mean=12.2°C-heating weeks
Photographs
4
Site summary
Read this summary in:

The northern arm of the Marsa Nakari house reef, a low-relief slope of coralline pavement and rubble with scattered coral patches and a hunting lionfish. It was severely bleached in September 2024, with about 57% of coral tissue affected, and Anderson's own dive computer read 31°C on the dive.

Max. depth dived
24.8 m
dive-log maximum
Water temp. during survey
31.5°Cii
+4.8°C vs the 2024 mean sea temperature (26.7°C)
ii Note: NOAA's regional station series averages 1.6°C warmer than the satellite pixel nearest this site (1.4 km away), which is used here instead.
Bottom time
55 min
in at 14:29

Fifteen independent survey stations shown with the program’s logo — click one to see how far it is from this site.

One other CRD dive site within 5 km shown in orange — click a marker to open its page.

3 of these 4 photographs are shown beside the text that discusses them under "Site description" below.

2

Photo credit & attribution

Site description

Setting

The northern arm of the Marsa Nakari house reef, dived on the afternoon of 20 September 2024 with Red Sea Diving Safari.

General benthic features

The reef is a low-relief slope of broad coralline-crusted pavement and rubble running out onto sand, with widely spaced coral patches on it — branching and corymbose Acropora, pocilloporids, Porites, faviids, encrusting Millepora-type fire coral, and one large partly overgrown giant clam shell set into the pavement.

Coral cover

Coral cover is 23.3% ± 14.0 across 195 photographs, quoted verbatim from Mayfield, A.B. (2025) Environments 12:248 — Red Sea 2023-24 bleaching; CoralNet point annotation, Appendix A — a manual, diver-annotated CoralNet point count from Anderson's own published work, not a computer vision output and not recomputed here.

Stressors

The site record reports 56.9% of coral tissue bleached at about 21.9°C-weeks DHW. Anderson recorded the water temperature himself: one frame is a wrist shot of his dive computer reading 31°C at 13:59. That single image is the most direct evidence anywhere in the set of what was driving the bleaching. Much of the pavement is old dead framework rather than recent loss, but scattered through it, in almost every wide-angle, are small stark-white colonies (e.g., Image 1, Image 3, Image 4).

1Image 13Image 34Image 4

Anderson's captions record what he found in detail: "badly bleached Acropora table", "bleaching Porites", "dead Pocillopora", "dead pocilloporid", "another dead pocilloporid", "dead Porites", "dead fire coral".

Fish and other fauna

A lionfish (Pterois-type) hunts the patches.

Comparisons with other data

This site also carries an external cross-reference to Reef Check's Marsa Nakari North station 0.25 km away (mean 38.0% hard coral over seven surveys, 2010–2025), reported side by side with the CRD figure and deliberately not averaged. Different station, different observers: a near-concurrent cross-check, not a repeat of this site.

Other notes

See flags.

CV model comparison

Computer vision on this site's own photographs gives In-house DINOv3 point classifier 42% — reported alongside rather than merged, because as of September 2026 no computer-vision method estimates coral cover accurately on new images.
Headline is the reference value; every other row is listed beside it for comparison and none is averaged in.
More infoThe reference row is this dive site's own published value (Mayfield 2025, Appendix A, 195 photos); the other rows are AREA-level (Marsa Nakari) comparisons, not run on this site's frames. ⚠ The comparison rows are REGIONS, not dive sites: the paper's main tables report cover by region, and this site's own value comes from its Appendix A. ⚠ The manual column and the CV columns are on DIFFERENT FRAME SETS: the published cover spans 674–1,180 frames, the CV arms ran on the 30- and 129-frame hand-scored reference subsets. CoralNet is n/a by design: the reference set IS the hand-scored set. DINOv3 is restricted to frames it never saw. CoralNet automated point classifier: n/a — the reference set IS the hand-scored set; these frames carry no independent CoralNet robot label to compare against CoralSCOP (SAM-based mask-sum), unedited photos: pending — CoralSCOP run: 370/747 images scored at build time CoralSCOP (SAM-based mask-sum), edited photos: pending — CoralSCOP run: 370/747 images scored at build time
MethodHard-coral cover (%)
Manual (published)23.3
In-house DINOv341.8
Claude27.7

Independent surveys nearby

Hard coral cover over time — this site and every independent station within 5 km. Programs are shown separately because they use different methods at different stations; the lines are not one comparable series.
0%17%34%51%68%200320142025Reef Check 2003: 39%Reef Check 2003: 49%Reef Check 2004: 48%Reef Check 2005: 23%Reef Check 2005: 33%Reef Check 2005: 43%Reef Check 2005: 48%Reef Check 2005: 61%Reef Check 2006: 9.4%Reef Check 2006: 49%Reef Check 2007: 11%Reef Check 2007: 22%Reef Check 2007: 39%Reef Check 2007: 47%Reef Check 2009: 49%Reef Check 2010: 35%Reef Check 2010: 37%Reef Check 2011: 39%Reef Check 2011: 46%Reef Check 2012: 44%Reef Check 2012: 52%Reef Check 2012: 53%Reef Check 2013: 14%Reef Check 2013: 22%Reef Check 2013: 30%Reef Check 2013: 31%Reef Check 2013: 43%Reef Check 2013: 53%Reef Check 2014: 4.4%Reef Check 2014: 6.2%Reef Check 2014: 46%Reef Check 2014: 50%Reef Check 2014: 52%Reef Check 2015: 40%Reef Check 2015: 41%Reef Check 2017: 53%Reef Check 2018: 37%Reef Check 2018: 40%Reef Check 2019: 59%Reef Check 2022: 53%Reef Check 2024: 40%Reef Check 2024: 47%Reef Check 2024: 51%Reef Check 2024: 58%Reef Check 2025: 27%Reef Check 2025: 29%Dr. Coral (CRD) 2024: 23%Year-averaged across all programs: no detectable trend (+0.16 pp per year, not separable from zero; 18 years)
Reef Check Dr. Coral (CRD)Year-average (no detectable trend)

Within 5 km, 15 independent survey stations recorded hard coral cover in 70 surveys between 2003 and 2025. Of the 10 stations surveyed in more than one year, 5 declined, 3 increased, and 2 changed by less than 5 percentage points between their first and latest surveys. The longest record, Marsa Nakari North (Reef Check, 0.25 km away), went from 35% in 2010 to 27% in 2025. Surveys since 2021 average 43% (range 27–58%, n=7). This site's own estimate (23%) is indistinguishable from the recent range (27–58%): the 3.6-point gap is inside the ±7 percentage-point noise between methods; the methods differ, so the comparison is context, not a like-for-like test.

Collected by other programs using different methods (Reef Check uses point-intercept transects), so these are context for the figures above, not a like-for-like comparison. Where a station was surveyed more than once the range is shown. Station names are not dive-site names.

Show all 15 independent survey records
Independent survey data near this site
AgencySite / locationDateHard coral cover (%)DistanceLink
Reef CheckSamaka Mogeha (North Marsa Nakari)2003–200543–49% (3 surveys)0.73 km—
Reef CheckCheckpoint2003–201322–43% (3 surveys)3.19 km—
Reef CheckMarsa Tondoba North2003–201439–53% (11 surveys)4.78 km—
Reef CheckMarsa Tondoba/3 Sisters2005–201239–61% (3 surveys)1.88 km—
Reef CheckGotta Nakari2005–20069.4–23% (3 surveys)2.56 km—
Reef CheckTondoba Bay, outer reef North2005–201422–46% (5 surveys)4.59 km—
Reef CheckMarkas Ratz South200711%4.61 km—
Reef CheckMarsa Nakari North2010–202527–47% (13 surveys)0.25 km—
Reef CheckMarsa Nakari South2010–202529–40% (14 surveys)0.44 km—
Reef CheckMarsa Um Tondoba North Entrance201314%4.69 km—
Reef CheckMarsa Um Tondoba- 3 Sisters201452%4.15 km—
Reef CheckMarsa Um Tondoba Lagoon20144.4%4.78 km—
Reef CheckMarsa Um Tondoba Fringing Reef North20146.2%4.78 km—
Reef CheckShaab Nakari, north-east side2017–202451–59% (6 surveys)2.77 km—
Reef CheckDream Lagoon Marsa Alam2022–202453–58% (4 surveys)1.93 km—

Data & links

All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics and the organizations named in the data-sources table above.

© Coral Reef Diagnostics.