Tonga - Vava'u (TOVA51)

Setting

Northwest end of Treasure Island, Vava'u: a leeward, lagoonal fringing reef (Anderson's sample sheet).

General benthic features

Two of the three habitat frames are views of the same thing: an extensive field of branching, staghorn-form Acropora, growing as an open interlocking thicket over a gently sloping bottom, with pale sand or rubble visible in the gaps between clumps and a few small knobby and encrusting colonies among the branches (e.g., Image 1, Image 2).

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In one the thicket runs continuously away into the haze with a diver working in the blue water above it; in the other it fills the foreground and continues past the edge of the frame. That is the whole of what the imagery establishes about this site's habitat — it does not show the reef's profile, its depth zonation, its shallower or deeper communities, or how much of the site the thicket occupies. The third frame records the key observation at this site: a tight aggregation of crown-of-thorns starfish, several individuals massed shoulder to shoulder with their arms fanned across a pale, bare patch of substratum, with green encrusting and foliose colonies around the edges of the frame (e.g., Image 3).

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Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• 35%, from the Khaled bin Sultan Living Oceans Foundation's in situ transect survey (Global Reef Expedition site data); the photographs illustrate the site. Algal cover is 37% of the benthos.
• Transect mean 35 ± 3.8% SE (n = 4 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean.

Stressors

Anderson recorded the frame as crown-of-thorns starfish (COTS). The aggregation itself is unambiguous; the frame cannot establish how far the outbreak extended or how much of the site had been grazed. The staghorn thicket in both wide frames is pale gray-white along most of its branches, with the corallites intact rather than bare skeleton: bleached, but still alive (e.g., Image 1, Image 2). Anderson's sampling sheet also records bleaching in the colonies sampled: two of the eight were 80% and 50% bleached, three more 5–10%, and one cream-pale and possibly unhealthy. The Living Oceans Foundation transects here recorded 0.5% cyanobacteria and no recently dead coral.

Comparisons with other data

James Cook University and the Ministry of Fisheries Tonga surveyed a nearby station (Euiki West side), 0.26 km from the pin; we could not confirm that it is the same reef. If you have survey data from this site to share, please email us.

Other notes

Photo review of 3 habitat frames plus 42 sampled-colony close-ups (Vava'u, 27 Sep 2013). The account on this page is written from the three habitat frames only; the colony images are treated purely as a record of what was sampled. Three frames is very little to describe a reef with, and all three are ambient-light shots at survey depth with heavy blue-green casts and no scale reference, so what follows is deliberately limited to what they actually show. Eight Pocillopora colonies were sampled here (colonies 98-105), six of them identified as P. acuta in Anderson's own field records; two (colonies 103 and 105), from which no RNA or DNA was extracted, are identified as P. damicornis on the sample sheet (not genotyped). The 42 close-ups are repeat polyp-scale macro, tag, and setting shots of only those eight colonies — numbered tags appear in frame, several held by a gloved hand — and describe the colonies, not the reef.