Tonga - Ha'apai (TOHA09)

Setting

Lagoonal patch reef. Low relief wide spurs with 20-40 cm relief. These slope from 3-4 m moderately steeply to 22 m, then a second reef system extends from the sand up to 20 m, slopes very gradually seaward to 23 m, then drops steeply to 30 m, ending in sand rubble at 31-33 m. The sand flat continues sloping seaward very gradually.

General benthic features

Shallows at 10 m have 10-15% live coral dominated by small massives especially Goniastrea and Platygyra and high numbers of small Montipora, small Porites, Cyphastrea, and other species. Soft corals make up 20% of the cover, turf covers 40%, and zoanthids carpet 20% of the substrate. Mid depths are dominated by Acropora, Goniastrea, Lobophora, Astreopora, and crusts of Favia up to 1.5 m wide. High amounts of turf algae throughout mid and deeper areas (60%) and 10% cyanobacteria between 10-20 m (a by-eye estimate; the transects recorded 3.7%), which disappears at 25 m. At 20-30 m there are numerous table acroporids, medium sized Lobophyllia, Montipora plate, and Coscinaraea plates, some 3-4 m across.

Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• Coral cover 25% (the expedition's in situ transects).
• Coral cover increases from 25% at 15 m to 30-40% at 20 m then declines progressively to 10% at 30 m.
• Coral Health Index 2.00/5 (Mayfield et al. 2021, Platax).
• Transect mean 25 ± 3.8% SE (n = 5 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean.

Stressors

Approximately 10% of the coral is dead in growth position. Between 2-5% of the table acroporids and Pocillopora show signs of white syndrome. The 2013 survey notes for this site record one Culcita cushion star (Khaled bin Sultan Living Oceans Foundation expedition site notes, 2013; regional summary in Bruckner 2014). The Living Oceans Foundation transects here recorded 3.7% cyanobacteria and no recently dead coral.

Fish and other fauna

Moderate numbers of sea cucumbers from 20-30 m.

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.

Dive record

TOHA09 (Ha'apai): surveyed 14 Sep 2013 during the Khaled bin Sultan Living Oceans Foundation Global Reef Expedition.

Other notes

Anderson was busy sampling corals at this site, so the site description comes from the Living Oceans Foundation survey team's site notes and benthic transect data. Those transects recorded 25% hard coral cover. Anderson sampled 8 Pocillopora colonies here, numbered 18 to 25 in the expedition series: the seven with photo folders are labeled Pocillopora acuta (2) and Pocillopora damicornis (5), and colony 20 is recorded on the sampling sheet as Pocillopora sp. The sheet notes three of the eight as 5–20% bleached and one more as pale and possibly unhealthy. The photographs shown for this site are close-ups of the colonies Anderson sampled, so nothing here describes the reef's habitat, structure, or condition from imagery.