N. GBR - Pink (AU61A61)

Setting

Global Reef Expedition station AU61A61 on Unnamed Reef 61A, far northern Great Barrier Reef (-13.3893, 143.9565), the first of Anderson's three dives on this reef on 13 September 2014. His notes describe a backreef site with interesting topography, "basically, a series of inter-connected bommies of varied heights and sizes"; the large bommies (more than 30 m across) were likely the ones surveyed by the other divers. Visibility was 5 m or less. This reef lies in a Preservation (Pink) Zone, the Marine Park's strictest, entry-restricted tier.

General benthic features

His bommie-versus-sand measurements put coral-based hard platforms and bommies at 57 ± 4.3% of the benthos in the 15 m sand apron, the deepest area within swimming distance of the reef, and Isopora was everywhere. Under the boat at 5-10 m, "the coral cover and diversity were both spectacular." On his transects at 14.5-15 m he recorded encrusting corals, branching acroporids, Pachyseris, plating Echinopora, an extensive Millepora thicket, Pocillopora damicornis, P. acuta, and Seriatopora hystrix, with at least 20 hard coral species on his first transect and 20-30 on his third, and he noted the absence of Stylophora pistillata at the site; his 9 m transect crossed an almost solid Acropora meadow (100% cover) that was very brittle and poorly cemented to the reef. The 18 posted frames from this dive show that bommie country in wide and mid-range views: steep bommie faces packed with branching, plating, and massive colonies rising into blue water (e.g., Image 3, Image 4, Image 6, Image 8, Image 11, Image 17); bommie tops crowded with plating and lobed massive colonies, soft corals, and bright yellow encrusting growth (e.g., Image 2, Image 5, Image 12, Image 13); a large, smooth lobed massive dome under a school of fusiliers (e.g., Image 9); tiers of tan plating colonies over fine branching thickets (e.g., Image 7, Image 10, Image 16); dense fine-branching thickets in cream and brown (e.g., Image 18); and coral-covered bommie bases on clean white sand (e.g., Image 14, Image 15).

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Image 1 looks across a slope of mixed colonies, with lobed pink and tan massive colonies in the foreground.

1

Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• The point-count survey read 53% live coral. Anderson's by-eye estimates on his four transects were 30-40% (14.5 m), 25-35% (14.5 m), 30-40% (15 m), and 100% across the 9 m Acropora meadow.
• Transect mean 51 ± 5.6% SE (n = 4 transects; Living Oceans Foundation per-transect benthic data); the headline above is the expedition's station value (the headline weights each depth equally; one depth had a single transect).

Stressors

Anderson's notes for this dive record no bleaching, disease, or crown-of-thorns starfish. He logged a blue-and-white branching coral on his third transect; the pale branching thickets in Image 16 and Image 18 are evenly colored from base to tip beside fully pigmented neighbors, and no paling is called from them.

Fish and other fauna

His notes list two or three small gray reef sharks. A school of fusiliers passes over the massive dome in Image 9, and a diver appears in Image 14 and Image 17.

Comparisons with other data

No other surveys have been conducted at this site to date. Within 5 km, one independent station, AIMS manta tow at SAND BANK NO 8 REEF, 3.45 km away, read 19–43% between 1993 and 2023.

Other notes

By their capture times, the 36 frames matched to this reef by boat GPS position and date belong to the second dive here (AU61A63), whose page carries them; this page describes its own 18 frames and Anderson's notes for this dive.