Coral Reef Diagnostics

Kenya - Trumpet Area (Watamu)

Global Fund for Coral Reefs (GFCR)
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05
Photo: Anderson Mayfield/Coral Reef Diagnostics
Country
Survey date(s)
2024-03-29
Coordinates
-3.4027, 39.9880
Coral cover
21%
Manual point count (193 photos) · other methods below
Observations
Heat stress
Today’s heat load
16 Sep 2026 · No heat stress
5-year thermal stress load
5-year mean max. degree heating weeks (DHW)
2021–2025
NOAA Coral Reef Watch — Kenya 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 infoKenya (NOAA CRW virtual station) · East African Coral Coast ecoregion mean=4.1°C-heating weeks
Photographs
4
Site summary
Read this summary in:

Trumpet Area is a low-relief reef flat off Watamu, named for a dense mid-water aggregation of trumpetfish and cornetfish that drifted over the reef during the survey. Coral sits as scattered colonies rather than continuous framework, and bleaching was severe (85.8% of tissue) across Acropora, massive corals, and even the leathery soft corals that form the flat's largest continuous stands - one frame is captioned 'bleached soft coral' by Anderson himself. Published cover was 21%; turtles and a peacock mantis shrimp were also recorded.

Max. depth dived
10 m
Water temp. during survey
32.3°C
+4.3°C vs the 2024 mean sea temperature (28.0°C)

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

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

Photo credit & attribution

Site description

General benthic features

The full 205-frame set confirms a low-relief reef flat rather than a wall or spur-and-groove: a broad algal-and-turf pavement with rubble, shallow sand pockets, and a few small undercut ledges, over which coral sits as discrete colonies rather than continuous framework. Wide shots taken minutes apart along the track look consistent -- there is no zone of dense, healthy coral anywhere in the set. Corymbose and digitate staghorn corals (Acropora) are the most numerous stony corals, occurring as scattered dinner-plate to arm-span colonies, and they carry the visible bleaching load: frame after frame shows them brilliant, uniform bone-white to the branch tips (frames 1, 24, 45, 75, 87, 101, 109, 114, 137, 143, 168, 180) (e.g., Image 2).

Large meandroid massives with worm-track ridges (a Platygyra-type morphology, one over a meter across) are the most conspicuous single heads and sit in an intermediate state -- pale lilac-white with residual host pigment (frames 46, 71, 121, 186) -- while other massives, including a cerioid Favites-type head and several small Goniastrea-type domes, are still solidly pigmented (frames 47, 165) (e.g., Image 1).

The largest continuous stands on the pavement are not stony corals at all but lobed and ruffled leathery soft corals (Sarcophyton/Lobophytum-type), which carpet whole sections of flat in several frames (3, 53, 76, 102, 106, 122-124, 176); these too are affected, ranging from healthy chocolate-brown through washed-out cream to one frame Anderson himself labeled "bleached soft coral" (e.g., Image 3).

Genuine foliose and plate stony corals are present but subordinate: tiered whorls, flat gray plates, and a large ridged Pachyseris-type sheet, most of them paled to cream (frames 92, 146, 163, 170, 171, 186). Between the corals the pavement is heavily algal: dense turf, maroon and crimson fleshy macroalgae, bright green segmented Halimeda (one frame is filenamed "too much Halimeda"), and pink crustose coralline crusts on rubble, with orange encrusting sponges scattered through.

Coral cover

Hard coral cover 21%, with 85.8% of hard coral tissue bleached -- the published CoralNet values from Mayfield (2025), not recomputed here. Coral cover 21% -- and 85.8% of hard coral tissue bleached (March-April 2024). Measured from 193 white-balanced photographs taken at this site during the 2024 Western Indian Ocean mass bleaching event and point-annotated in CoralNet, published in Mayfield, A.B. (2025) A Citizen Science Approach for Documenting Mass Coral Bleaching in the Western Indian Ocean. Environments 12(8):276. doi:10.3390/environments12080276.

Stressors

A handful of tabular and corymbose Acropora remain fully brown or golden-tan (frames 56, 108, 136, 190), and several colonies are caught mid-transition with white tips over a pigmented base, so the response is colony-specific as well as growth-form-specific. Submassive and encrusting Porites-type mounds appear both fully pigmented and stark chalk-white within the same frame (frames 110, 111). Partial mortality is already visible on the biggest colonies -- bare skeleton furred with turf or bound by algal film across the top of encrusting sheets and one massive head (frames 88, 98, 199). Typical recent thermal stress for the ecoregion is a mean annual maximum of 4.1 degree-heating weeks (2021-2025, NOAA Coral Reef Watch, East African Coral Coast); in 2024 NOAA recorded a Kenyan peak of 13.5 DHW on 18 April, the highest since records began in 1985, and in situ temperatures ran about 1.3 C above NOAA's estimates, so true heat stress was likely nearer 22 DHW. No crown-of-thorns starfish (COTS) or other corallivores evident.

Fish and other fauna

The site is named for the fish: between about 11:29 and 11:30 a dense aggregation of trumpetfish/cornetfish hangs in mid-water and drifts over the flat, and eight consecutive frames are given over to it. Turtles were photographed on at least two separate encounters (11:15-11:19), one resting among leathery soft corals and one grazing the algal pavement. A peacock mantis shrimp (Odontodactylus scyllarus) was shot at close range in coralline-crusted rubble, and a small reticulate yellow-and-dark dorid nudibranch gets three macro frames at 11:40 (e.g., Image 4).

Also present: a blue sea star, a pale lobed fungiid, Moorish idols, bannerfish, powder-blue surgeonfish, a bluestripe snapper, and damselfish and chromis holding position over the coral heads in nearly every wide shot.

Comparisons with other data

No independent survey was made at this exact site; the nearest ones are listed in the table below.

Dive record

Surveyed 29 March 2024, roughly 11:04 to 11:57 at about 10 m off Watamu, during the 2024 Western Indian Ocean mass bleaching event; the topside frame shows the dive boat Mrembo on a flat, sunlit sea. Surveys were run with Extra Divers.

CV model comparison

Computer vision on this site's own photographs gives In-house DINOv3 point classifier 35%; CoralSCOP 21% — 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.
MethodHard-coral cover (%)
Manual (published)20.8
CoralNet20.8
In-house DINOv335.2
CoralSCOP unedited20.7

Independent surveys nearby

Data availability near this site
Agency / programYear(s)Stations / distanceLink
McClanahan et al. 201620163 stations, 2.12–2.24 kmRecords ↓
WCS Kenya via MERMAID2014–20243 stations, 2.47–4.38 kmRecords ↓
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%10%20%30%201420192024WCS Kenya via MERMAID 2014: 20%WCS Kenya via MERMAID 2022: 8.8%WCS Kenya via MERMAID 2024: 16%McClanahan et al. 2016 2016: 23%McClanahan et al. 2016 2016: 24%McClanahan et al. 2016 2016: 28%WCS Kenya / WCS Tanzania via MERMAID 2024: 15%Dr. Coral (CRD) 2024: 21%Year-averaged across all programs: no detectable trend (-0.91 pp per year, not separable from zero; 4 years)
WCS Kenya via MERMAID McClanahan et al. 2016 WCS Kenya / WCS Tanzania via MERMAID Dr. Coral (CRD)Year-average (no detectable trend)

Within 5 km, 6 independent survey stations recorded hard coral cover in 14 records between 2014 and 2024. Of the 1 station surveyed in more than one year, 1 increased between their first and latest surveys. The longest record, Watamu (WCS Kenya via MERMAID, 2.47 km away), went from 8.8% in 2022 to 15% in 2024. Surveys since 2021 average 13% (range 8.8–16%, n=3). This site's own estimate (21%) is indistinguishable from the recent range (8.8–16%): the 4.9-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 (MERMAID is a data platform: each MERMAID row names the organization that did the survey, and its method is in the row's hover text), 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.

Independent survey data near this site
AgencySite / locationDateHard coral cover (%)DistanceLink
WCS Kenya via MERMAIDWatamu Tewa201420% (2 images)3.51 kmDarling E. 2018. Kenya CRCP legacy. MERMAID
McClanahan et al. 2016Watamu South (Kenya)201623%2.12 km—
McClanahan et al. 2016Watamu south (Kenya)201628%2.12 km—
McClanahan et al. 2016Watamu north (Kenya)201624% (2 surveys)2.24 km—
WCS Kenya via MERMAIDWatamu2022–20248.8–15% (2 images)2.47 kmDarling E, Kosgei J, McClanahan T, Muthiga N, Oddenyo R. 2022. Kenya-Marine Monitoring_2022. MERMAID; Hassan J, Julius P, Mensa J, Mkwavila S, Musembi P. 2024. Miamba Yetu Program - Kenya & Tanzania. MERMAID
WCS Kenya via MERMAIDWatamu (mean of 6 surveys, 2008–2024)202416% (6 images)4.38 kmDarling E. 2018. Kenya CRCP legacy. MERMAID

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.