Tonga - Ha'apai (TOHA03)

Setting

The site is not uniformly low-relief: it has locally dense, high-relief Acropora stands as well as the sparse ground. The undercut structure recorded in the survey notes shows up directly: Image 13 and Image 11 look along a ledge with a dark overhung recess beneath a coral-crowned lip, and Image 5 looks up the flank of a mound built of stacked plating and branching colonies from the channel below.

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Image 4 is the poor-visibility frame — a diver hanging in green-gray water over a steep, dimly resolved wall — and stands as the honest counterweight to the clear frames.

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General benthic features

Two frames are given over to a single enormous mound blanketed in branching and staghorn Acropora, branch tips reaching almost to the surface, so completely covered that no substrate shows — a structure Anderson described as an Acropora mountain and photographed a second time from further back with the whole mound rising out of a rubble apron (e.g., Image 8, Image 9).

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A third frame Anderson calls an Acropora garden: open, well-spaced arborescent colonies across the mound top with a thick cloud of small planktivores hanging over them against blue water (e.g., Image 10).

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A fourth frame centers on a broad pale table Acropora on a dark mound flank with staghorn stands behind it (e.g., Image 17).

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The mound tops themselves are a crowded low-relief mosaic — small mauve and pink corymbose Acropora and Pocillopora, tan corymbose and digitate colonies, encrusting and submassive Porites-type mounds, mauve plating colonies, and coralline-crusted pavement between them, with sand pockets and loose rubble threading through (e.g., Image 6, Image 7, Image 11, Image 14, Image 15, Image 16).

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Fleshy soft corals are a genuine component and not an incidental one: mustard-yellow and gray-green lobed and digitate colonies (Sinularia/Lobophytum-type) run through the foreground of the frame Anderson simply calls a soft coral garden (e.g., Image 12) and recur in Image 15, Image 7, and Image 16.

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Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• Coral cover 20%, 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.
• Transect mean 20 ± 4.0% SE (n = 5 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean.

Stressors

Standing dead branching skeletons and bare rubble appear in several mound-top frames, but no bleaching, disease lesion, or crown-of-thorns feeding scar is visible in any of the 17 frames. The Living Oceans Foundation transects here recorded 0.4% cyanobacteria and no recently dead coral.

Fish and other fauna

Two frames are a banded sea snake, which Anderson identified, one photographed alone as it tracks across coralline rubble and sand and one with a diver in the frame; that field identification is used here.

Comparisons with other data

Apart from the Living Oceans Foundation survey shown here, we found no other surveys at this site as of 2026. Within 5 km, one independent station, Reef Check at Kito si'I, 2.11 km away, read 18% in 2002.

Other notes

The site's photographs show shallow mound tops and rubble, and also the site's most striking structure. What the set still cannot show is the deeper channel slope and the 18 m sand base in the survey notes — the frames stop on the mounds and their immediate flanks.

Survey team's site notes: Shallow, 1-3 m flattopped mounds separated by sand channels up to 3 m below top. They are undercut with small caves and ledges and high abundance of Tubastraea and smaller plating corals under overhangs. Sides of channel slope steeply to 18 m, ending in sand. Sand continuous out getting progressively deeper; soft bottom has large ripples and depressions from waves and currents and low cover of Halophila sea grass.