Australia (GBR) - Far North: Green stations (no-take reefs)

Spalding et al. (2001) single out the ribbon reefs as the defining feature of the northern Great Barrier Reef. Beyond Raine Island the shelf is generally less than 50 km wide, and along its outer rim long, slender reefs, mostly under 500 m across and up to 25 km in length, are strung out between narrow passes, with water deepening past 1,000 m only a few hundred meters seaward. In the northernmost 80 km or so of this line, sediment swept through the passes by strong currents has built delta-like formations on the sheltered side, which then became a base for new reef growth. Shoreward are mid-shelf and inner-shelf reefs, and fringing reefs that border the mainland directly. The South Equatorial Current divides on reaching the shelf: a weak branch, the Hiri Current, runs north above roughly 14°S, and the East Australia Current carries water south. The atlas records most of the reef's 350 or so coral species from the northern GBR and estimates Australia's national reef area at about 48,960 km²; Souter et al. (2021) give 35,487 km² for the GCRMN subregion made up of the Torres Strait–northern GBR, central–southern GBR, and Tweed–Moreton ecoregions. When the atlas was written, only about 5% of the Marine Park was closed to fishing, though that share took in more than 120 reefs; Wilkinson (2006) reports that in mid-2004 the Australian Parliament extended highly protected, no-take status to 33% of the GBR World Heritage Area.

According to Souter et al. (2021), the 2016 bleaching did the most recent damage to these northern reefs, killing an estimated 30% of shallow-water coral in the northern third of the GBR, with effects detected as deep as 40 m. Earlier bleaching was less focused on the north: the 1998 event was mostly confined to inshore reefs, the 2002 event reached offshore reefs as well, and the central GBR was the most affected both times. Coral cover in the Torres Strait and northern GBR increased between 2002 and 2008. Since 2009, eight severe cyclones have struck the GBR, and crown-of-thorns starfish have erupted periodically since the early 1960s, most recently from 2010 in the Cairns–Cooktown section. By 2019, the GBR-wide mean for hard coral cover stood at 24%, down from about 34% in the late 1990s.

This unit covers the 54 far northern Great Barrier Reef stations coded Green in Anderson's 2014 survey set. The unit is the expedition's Green stratum, its no-take reefs: Marine National Park (Green) Zone reefs plus Yonge Reef, which the Zoning Plan designates a Scientific Research Zone (no-take, research by permit) with a Conservation Park Zone on its lee side (AUYG37-42). On the zoning map four positions on the Ribbon Reef 7 and Yonge Reef edges (AUR701, AUR702, AUR703, AUYG38) fall a few tens of meters into the adjoining Buffer Zone. The stations spread from about 11 to 15.3°S and were surveyed by in situ transect between 3 September and 1 October 2014, mostly at 5-9 m; recorded depths ran from 4.9 m at AU3480 (the other expedition team's survey depth) to 24.1 m at AUWO103 on Wood Reef. Named reefs include Lark, Monkman, Siddons, Wood, and Yonge Reefs, Ribbon Reef 7, the area near Hilder and Eyrie Reefs, and Unnamed Reefs 34, 74, and 11-096.

The settings vary widely. On Unnamed Reef 34, a steep wall dived in a 1.5-knot current (AU3483) carried Turbinaria, Porites, Diploastrea, and plating corals at close to 100% cover by eye at 3-5 m, while silty neighboring dives turned to rubble by 10 m (AU3479) or sand below 17 m (AU3481). Siddons Reef has level Acropora meadows hundreds of meters wide, with staghorn and elkhorn colonies over 10 m long. On Monkman Reef, Pavona cactus carpets the 4-8 m band. At Wood Reef, a slope, a bommie field, and a second platform drop past 35 m, and the second Wood Reef dive (AUWO105) crossed dense Acropora cover with schools of jacks, barracuda, and wahoo. Ribbon Reef 7 has a windward slope to 25-30 m and, on its leeward side, bommies rising from sand.

Transect cover ranged from 1.8% at AULK30 and 4.0% at AULK22 on Lark Reef to 79% at AU74147 on Unnamed Reef 74. On Lark Reef, 90% or more of the staghorn framework was dead. That is where the expedition's first crown-of-thorns starfish were found, but Anderson judged that the die-off predated them. Needle coral (Seriatopora) was the recurring warning. About 95% of colonies were bleached at Wood Reef station AUWO103, and nearly all were pale or bleached at 20-25 m on Ribbon Reef 7's windward face. Needle coral was healthy, however, at AUSD133 and AUWO105. Crown-of-thorns damage was recorded at 14 m at AU74151 and at about 15 m at AU74147 on Unnamed Reef 74, and starfish at AUSD131 (one) and AULK21, where several colonies in Anderson's frames are also stark white (no extent estimated). At AU3479 the 10 m rubble was blanketed in clay silt and fleshy macroalgae. Silvertip and gray reef sharks, Malabar groupers, cuttlefish, and benthic comb jellies at Siddons Reef were among the sightings.