Kenya - Reefolution nursery (Shimoni-Wasini)

Setting

Visibility is not uniform across the set. A large block of frames is green, milky, and heavily particle-laden with only a few meters of horizontal range, but many others — the tree frames, the tabular-Acropora arrays, several reef panoramas — are shot in blue water with the far end of a nursery structure still resolvable, so the day ranged from murky to reasonably clear rather than being uniformly bad.

General benthic features

The nursery is more varied than a single frame suggests. Four distinct kinds of structure appear. (1) Rope trees: vertical trunks with horizontal steel cross-bars, fragments hung on individual short droppers — exactly the hanging-nursery design, photographed repeatedly (e.g., Image 1).

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(2) Rigid welded rebar frames and A-frame tables with fragments fixed directly onto the bars, several now carrying grown-out branching and tabulate Acropora that has fused across the metal. (3) Cast concrete modules — squat cylindrical plinths, tiered "cake-stand" and stepped ziggurat blocks, and long ladder-like concrete beams with small fragments cemented onto the upper faces. (4) A bottle-and-cement substrate carrying fire coral, Millepora, in mustard-yellow branching plates (e.g., Image 20).

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The mature end of the program: three tiers of broad tabulate Acropora plates, each a meter or so across, stacked above one another on the array in open water. The natural reef around the array is a low-relief carbonate hardground with heavy macroalgal load. Whole frames are given over to brown fleshy algae — Sargassum and Dictyota-type turf — overtopping the substrate (e.g., Image 21).

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The stony fauna on it splits sharply by growth form. Foliose and encrusting agariciids, Galaxea with brown-and-white tipped tentacles, and mustard Turbinaria plates round out the assemblage. Soft corals and a pigmented purple-brown Tridacna giant clam are among the few saturated colors in the wide shots.

Coral cover

• Reference: Mayfield (2025)
• Data file: (Mayfield, 2025-Supplemental File S1)
• CoralNet submission package (accession #4963)
• Coral cover 40% — and 73% of hard coral tissue bleached (March-April 2024).
• Measured from 258 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, and it covers the natural reef as photographed — it is not a measure of nursery stock.

Stressors

Nursery stock condition is the interesting part, and it is patchy rather than uniformly bad. Across the array most fragments and grown-out colonies are pigmented — dense tan, gold-brown, and rust-brown Acropora, some corymbose, some staghorn, some tabulate, several with pale-blue or white growing tips that read as growth rather than bleaching. Against that, individual colonies and whole droppers are stark white with corallite structure still crisp and no algal film — bleached but alive — and the two states sit side by side on the same bar at the same depth. One frame catches it best: one table half rust-brown and half bone-white along a sharp margin. A minority of frames show the failure end of the range: one nursery tree where most droppers hang bare or carry only pale stubs (e.g., Image 22), and one with whitened fragments on an otherwise stripped bar.

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So the picture is neither "the nursery was fine" nor "the nursery was dying" — on this day, on these structures, bleaching was strongly colony-by-colony. Massive Porites domes, some several meters across, are still fully pigmented in dull olive, gold, and tan and appear repeatedly (e.g., Image 3).

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Meandroid brains — Platygyra and relatives — are mostly bone-white with the ridge-and-valley surface intact (e.g., Image 23, Image 2), though one frame shows a fully pigmented pink-and-cream Platygyra a few frames away (e.g., Image 24).

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Lobophyllia is bleached white with the fleshy lobes still turgid (e.g., Image 25, Image 26).

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Branching Acropora and Pocillopora on the natural reef carry heavy apparent damage: fields of white staghorn (photos not shown), white corymbose colonies (e.g., Image 27), and a bleached bushy Seriatopora (e.g., Image 17), plus pocilloporids that are past bleaching and into death, their skeletons furred with turf (e.g., Image 28).

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Anemones are conspicuously affected — several large host anemones are white to blush-pink with tentacles extended, one still holding an anemonefish. Because the frames are color-adjusted, bleaching here is called on structure, not on hue: bare white surfaces with crisp corallites and no algal film (bleached, tissue alive), against dull white or gray surfaces already furred with turf and red algae (recently dead). Both are present, side by side, and the split between them is the clearest signal in the set. One frame shows a pale plating colony with black, branching dead portions. Typical recent thermal stress: mean annual maximum of 4.9 degree heating weeks (2021-2025, NOAA CRW; Kenya virtual station). Seawater here was an estimated 32.0°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 recorded a peak of 13.5 degree-heating weeks on 18 April 2024, the highest for Kenya since records began in 1985. 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. No crown-of-thorns starfish (COTS) or other corallivores were evident.

Fish and other fauna

Fauna seen around the array: a flying gurnard fanning its wings on sand, a blue-legged hermit crab seen twice, a pufferfish, a giant clam, and divers working the array.

Comparisons with other data

REEFolution Kenya surveyed a nearby station (Pilli Pipa Restaurant) between 2018 and 2023, 0.24 km from the pin. Within 5 km, nineteen independent stations (REEFolution Foundation, WCS Kenya via MERMAID, and submitted to MERMAID by Kosgei J, Musembi P.*) recorded hard coral cover between 2010 and 2024: six by benthic survey, station-year means of 0.0–66%, and thirteen by MERMAID bleaching-protocol quadrats, station-year means of 18–55%; the nearest, REEFolution Foundation at Pilli Pipa Restaurant, 0.24 km away, read 4.9–56% between 2018 and 2023.

Dive record

Dived 20 March 2024 in the Shimoni-Wasini channel, on and around REEFolution's restoration site, at the height of the 2024 Western Indian Ocean mass bleaching event. Surveys were run with REEFolution.

Other notes

This description draws on 206 of the 276 frames on file, and the site turns out to be two things photographed together: an engineered nursery/outplant array, and the natural fringing reef it sits on. Roughly thirty frames are close-focus macro of pocilloporid and acroporid polyps, mostly pale to white and many soft-focus; three are blue-light fluorescence images (a green-glowing meandroid brain, glowing polyp mouths, an anemone) and carry no cover information at all.