Tonga - Ha'apai (TOHA14)

General benthic features

The wide frames show a densely built, high-cover reef. One looks up a slope crowded with lilac and violet corymbose Acropora, several stacked pale gray Acropora tables 40-80 cm across, staghorn branches, and a tan massive colony with meandering valleys on the right (a Platygyra or Leptoria growth form), while a loose school of dark white-tailed damselfish hangs in deep blue water above the crest (e.g., Image 21).

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Another is a tight view of the reef top with essentially no bare substrate: gray-lilac corymbose acroporids packed edge to edge, a clean Acropora table around 50 cm at center, gray mushroom-shaped and lobate soft corals, pale plating colonies, and dark maroon encrusting growth filling the gaps (e.g., Image 2).

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Another shows a broad staghorn-dominated field under a dense aggregation of dark damselfish and surgeonfish — a fitting image for a site where the survey specifically noted many damselfish algal lawns in the staghorn thickets — with pale and purple-brown branching Acropora, yellow-tipped corymbose colonies, and a tan massive Porites in the foreground, and turf-darkened dead branch sections mixed in Image 28.

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The dominant architecture across the set is corymbose and digitate Acropora in lilac, violet-gray, and pale tan, packed shoulder to shoulder over the reef top (e.g., Image 21, Image 10, Image 8, Image 5, Image 4, Image 24, Image 23, Image 11, Image 16, Image 32, Image 25, Image 17, Image 18, Image 35).

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Staghorn-form Acropora thickets recur throughout, sometimes as clean pale branches (e.g., Image 36, Image 22, Image 19, Image 26) and sometimes as darker, turf-shaded branch fields with dead sections mixed among live tips (e.g., Image 7, Image 30, Image 22, Image 28).

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Tabulate acroporids appear repeatedly as discrete plates 40-80 cm across sitting proud of the corymbose matrix (e.g., Image 8, Image 2, Image 20, Image 32, Image 18); one frame (Image 34) holds a single smooth gray-brown table roughly a meter across with a clean growing margin, perched on the reef edge against open blue water, and a second broad plate of similar form dominates (e.g., Image 38).

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Massive corals are present but secondary: tan and olive-green domes with meandering or cerioid surfaces (a faviid-type growth form) and low submassive Porites-like mounds sit in the gaps (e.g., Image 9, Image 2, Image 11, Image 15, Image 32, Image 26).

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Encrusting and plating growth — ruffled gray-white plates, dark maroon-brown encrusting sheets, and pale foliose margins — fills much of the remaining substrate (e.g., Image 37, Image 2, Image 3, Image 32, Image 1).

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Two color elements recur. Mustard-yellow to chartreuse encrusting and short-branching growth appears in several frames on the terrace (e.g., Image 37, Image 14, Image 13, Image 25), and low gray and gray-green lobate and mushroom-form soft corals with tan lobed capitula are scattered through the reef top (e.g., Image 37, Image 2, Image 32, Image 26).

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The photographs cannot separate the yellow growth from a hydrocoral (Millepora) versus a yellow Porites or encrusting Montipora, and this station's survey notes do record extensive Millepora deeper on the wall — so the identification is left open here rather than asserted.

Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• Coral cover 44%, from LOF-GRE in situ transects (the mean of all of this station's own transects in the expedition's per-transect benthic data) — a diver transect measurement, not a photographic or computer vision estimate.
• Almost all frames are shot obliquely upward from below the crest, so they exaggerate the vertical profile of the reef and are not planar views — none of them can be used to derive a cover figure, so the computer-vision rows below are a methods comparison, not a cover estimate.
• Transect mean 44 ± 5.7% SE (n = 6 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean.

Stressors

No bleaching is visible in any frame. What the frames do not settle: no frame shows an obviously bleached, stark-white colony, and no recent mortality scar large enough to read is visible, but many colonies photograph pale gray-lilac under flat ambient light and that is a color-rendering effect, not a health call. Dead, turf-covered branch sections inside the staghorn thickets (e.g., Image 7, Image 28) indicate normal background branch loss, not an event. A large table, which Anderson identified as an acroporid, is healthy but carries about a dozen small white spots, possibly feeding scars; no corallivore is visible (e.g., Image 34). The Living Oceans Foundation transects here recorded 2.3% cyanobacteria and no recently dead coral; they carry no bleaching, disease, or crown-of-thorns field.

Fish and other fauna

The detail shot is the best single record here: a giant clam (Tridacna) with a boldly mottled olive and black zigzag mantle wedged into the framework, a second dark speckled clam mantle just below it, salmon-pink encrusting sponge, an orange encrusting invertebrate, ruffled gray plates, and small blue-gray soft corals — a crowded, healthy-looking cryptic community (e.g., Image 1).

Fish are conspicuous in most frames: loose to dense clouds of dark, white-tailed damselfish and small planktivores hang over the crest in the majority of the wide shots (e.g., Image 21, Image 14, Image 13, Image 12, Image 9, Image 8, Image 4, Image 30, Image 6, Image 25, Image 17, Image 29), with the heaviest aggregations in two frames where Anderson noted large numbers of fish over the reef (e.g., Image 29, Image 6).

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Larger-bodied fish (surgeonfish- and wrasse-sized silhouettes) pass over the reef in a few frames (e.g., Image 5, Image 25).

Comparisons with other data

Apart from the Living Oceans Foundation survey shown here, we found no other surveys at this site as of 2026. If you would like to share yours, please email us.

Other notes

This is not a sampled selection: almost every frame is a wide reef-scale view of the same shallow terrace and crest, shot upward or along the slope into blue water, and the set is remarkably consistent from frame to frame — a continuously built reef surface with very little exposed pavement or rubble anywhere in it. Anderson's field verdict on the site was very high coral cover on an exceptionally beautiful reef (e.g., Image 21, Image 31, Image 19, Image 17, Image 18, Image 28).

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Four frames are overexposed or backlit: Image 35, the strongly backlit fish silhouette (e.g., Image 29), and the surface-glare frames over the crest (e.g., Image 7, Image 5). Depth is not resolvable from the imagery; all of it reads as shallow terrace and crest rather than the deeper wall described in the survey notes.

Survey team's site notes: Reef has a shallow terrace that slopes gradually from 4-8 m over about 100 m, then a steep slope from 10 m to 25 m, then a more gradual slope. At 5 m the dominant corals are staghorn thickets 1-5 m wide, digitate acroporids, small to medium table acroporids, Pocillopora, and numerous small to medium massives. The wall also had large areas of Millepora that was 20-40% cover at 15 m declining to 10% at 20-25 m. Coral cover dropped significantly below 15 m to about 10% dominated by small to medium Acropora, Pocillopora, with larger plates of Mycedium, Echinophyllia, and Montipora (50-200 cm), submassive Porites lobata (up to 1 m across).