N. GBR - Green (AUYG39)

Setting

The second Yonge Reef dive of 9 September 2014 explored the gentler, leeward face: a sloping sand apron scattered with bommies, stepping down from the crest through a 12-19 m bommie field before the reef fell away beyond 25 m. The expedition surveyed Yonge Reef as one of its Green (no-take) reefs; under the GBRMPA Zoning Plan the reef is a Scientific Research Zone (no-take, research by permit) with a Conservation Park Zone on its lee side, and the recorded position lies inside the Scientific Research Zone.

General benthic features

The photographs are bommie-top portraits. One shows a head crowded with mounding Porites, yellow faviids, and mixed small colonies with fish strung out into the blue behind it; another is a crest so densely packed with small branching colonies that the rock disappears, an urchin wedged in among them and a diver's fin in the corner (e.g., Image 3, Image 4).

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Seen side-on, another bommie top is carpeted the same way, a continuous mat of small branching colonies rising into the blue with a dark feather star among them (e.g., Image 7).

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A close frame catches the color range at this site: a violet knobby Stylophora-type colony, chartreuse digitate Porites, cream corymbose Acropora, and a blue-gray feathery octocoral within a hand's span of each other (e.g., Image 2).

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On the survey line, the tape runs between a pale pink and a lilac branching colony, over a blue-gray encrusting colony and small yellow knobby colonies (e.g., Image 6).

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A brain coral and red algal crusts fill out a fourth (e.g., Image 1), and a lower head carries rounded massive mounds, small corymbose and branching colonies, and bright red encrusting growths, with fish strung out over the slope beyond (e.g., Image 5).

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Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• Point-count cover measured 36%, and Anderson's single 50-m transect run across the bommie field found hard coral-based structure making up 48% of that sand-apron zone.
• Transect mean 40 ± 8.1% SE (n = 5 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

No bleaching, disease, or crown-of-thorns starfish were noted.

Fish and other fauna

The standout sighting was a large cuttlefish at 20 m.

Comparisons with other data

No other surveys have been conducted at this site to date. Within 5 km, eight independent stations recorded 3.9–66% hard coral cover between 1993 and 2023; the nearest, XL Catlin Seaview Survey at transect 12005, 0.90 km away, read 5.9–17% between 2012 and 2017.