Kenya - Kisite National Park-site 4 (Kisite National Park)

Setting

Water is clear and blue in the deeper wide frames and hazier and green-cast over the shallow reef flat. Relief is real: discrete bommies rising off sand with fish clouds over them, and between them broad low-relief hardground of turf, rubble, and coralline pavement.

General benthic features

The 72 reviewed frames show a shallow, high-cover coral garden of almost continuous knobby columnar coral, photographed while nearly all of it was white. The reef itself is dominated to an unusual degree by one growth form: dense, knobby-to-columnar coral in continuous hummocked sheets that run out of frame in every direction. About a third of the set (21 frames) is this one habitat. Anderson identified this coral as Galaxea in two of the frames: one is a wide shot of exactly this field, and another is a single colony of it in close-up with the polyps still extended; neither frame is among the four published here. Massive Porites is present as discrete lobate boulders rather than as the matrix, and meandroid Platygyra brains appear as isolated domes. Corymbose and digitate Acropora sit on the pavement between the Galaxea sheets, cauliflower-form Pocillopora is woven through, and Plerogyra bubble coral, foliose plate corals, and cream leather corals round out the assemblage. Three frames are the most colorful in the set, with pink and tan soft corals, red and yellow sponges, and gold crinoids among the pale coral. Between the coral, the pavement carries heavy turf and dark red fleshy macroalgae.

Coral cover

• Reference: Mayfield (2025)
• Data file: (Mayfield, 2025-Supplemental File S1)
• CoralNet submission package (accession #4963)
• Coral cover 46% — and 89% of hard coral tissue bleached (March-April 2024).
• Measured from 71 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.
• This is a published diver-photograph point-annotation value, not a computer vision estimate.

Stressors

On bleaching the set is emphatic, and it is emphatic on structure, not just on color. One frame is a whole hillside of columnar coral gone uniformly white from the bottom of the frame to the ridgeline against open blue — a snowfield (e.g., Image 2).

2

A wide frame of the Galaxea field shows the same thing. The Galaxea sheets read white to pale gray-lavender across the wide frames, with whiteness carried unbroken across entire colony surfaces rather than in patches, which is the pattern of thermal bleaching rather than of shading or camera cast. The discrete taxa follow suit: one frame is a large Platygyra dome gone chalk-white with dead eroded depressions already opening on its upper surface; another is a meter-scale lobate Porites bleached pale gray-lavender with only small brown remnant patches; a third is a Plerogyra with every vesicle stark white; the close-up Galaxea is white with tentacles still fully expanded, i.e. alive and bleached rather than dead. Branching Acropora is the most absolutely white group in the set, and the cleanest evidence is within-frame contrast rather than absolute color: one frame is a single bone-white corymbose colony sitting inside a ring of dark red-brown fleshy macroalgae, and five others all show white branching colonies against dark turfed rock in the same exposure (e.g., Image 3).

3

Two close-ups explain why the published figure is 89% of tissue and not 100%. Both are macro views of the knobby coral in which each individual knob is bleached white or pale pink at its margins but still carries a dense gold-yellow polyp center. Tissue is present and partly pigmented at the polyp scale on colonies that read as fully white from a meter away. The same partial retention shows at colony scale in one frame, where paling mauve-white lobes sit beside knobs holding faint tan. A minority of the reef kept obvious pigment, and it is worth naming because it is the exception. One frame is an olive-and-gold branching bommie beside the diver, plainly pigmented in the same frame as pale surroundings. Another is a bommie of salmon-orange knobby colonies (e.g., Image 1).

1

A third is a dark gray-purple encrusting dome on otherwise pale pavement. A fourth is a dark red-brown foliose plate. One more frame is a broad field of cream-tan ruffled leather corals, and another a deep maroon soft coral on sand — both show soft corals holding color, while a pale nephtheid soft coral (which Anderson identified as a cauliflower soft coral) is white-pink throughout (e.g., Image 4), so bleaching of soft corals alongside the stony corals is only partly supported.

4

Crown-of-thorns predation is directly documented here in four frames. In every one the animal is draped directly onto white bleached coral, surrounded by pink fleshy macroalgae and red sponge — predation stacked on top of thermal stress. The frames are mutually consistent with one or two individuals photographed repeatedly rather than an outbreak, and should not be read as four animals. Outright mortality is in the set too. One frame, which Anderson labeled as dying coral, shows an elongate mound of fine branching coral being smothered by cyanobacteria. The bleached Platygyra dome has open dead patches. Typical recent thermal stress: mean annual maximum of 5.1 degree heating weeks (2021-2025, NOAA CRW; Tanzania virtual station, whose polygon covers the Kisite-Mpunguti area). Seawater here was an estimated 31.6°C during the survey (read from the TG7 underwater camera and not validated, per Mayfield 2025, Environments 12:276, Table 1; the Kenya survey-wide mean of 32.0°C matched the 1998 event), and NOAA's Kenya virtual station recorded a peak of 13.5 degree-heating weeks on 18 April 2024, a level not reached there before in records going back to 1985; the Tanzania virtual station that covers this reef peaked at 16.0 on 16 April 2024. For the 2024 Kenya survey as a whole, Mayfield (2025, Environments 12:276) estimated that in situ temperatures ran about 1.3°C above NOAA's, so that "nearly 22 DHWs may actually have transpired"; those in situ readings came from the TG7 underwater camera and have not been validated.

Fish and other fauna

Other fauna recorded: a Phyllidia nudibranch, blue-gray with yellow tubercles, in three frames; a purple-and-orange Pseudoceros flatworm in three frames; a giant clam with a fully pigmented dark maroon mantle — notable because it held color while the corals around it did not; dense clouds of damselfish and orange anthias over the bommies; and butterflyfish over the reef top.

Comparisons with other data

WCS Kenya surveyed a station named Kisite, 3.38 km away (data via MERMAID). Within 5 km, twenty independent stations recorded hard coral cover between 2008 and 2024: eight by benthic survey, station-year means of 0.0–53%, and twelve by MERMAID bleaching-protocol quadrats, station-year means of 20–56%; the nearest, WCS Kenya / WCS Tanzania via MERMAID at Mkwiro, 0.57 km away, read 29% in 2020.

Dive record

Dived 21 Mar 2024 in Kisite Marine National Park during the 2024 Western Indian Ocean mass bleaching event. Surveys were run with REEFolution.

Other notes

Two frames put a diver in the scene for scale.