Australia (GBR) - Far North: Pink stations (Preservation Zone reefs)

The northern Great Barrier Reef, as Spalding et al. (2001) describe it, lies on a narrow continental shelf, usually under 50 km wide north of Raine Island, whose outer edge is marked by ribbon reefs: slender reefs a few hundred meters wide and up to 25 km long, perched on the shelf break and separated by narrow passes. Inside that outer line are mid-shelf and inner-shelf reefs, wide submerged Halimeda banks, and some of the few fringing reefs on the GBR that directly adjoin the mainland. Raine Island, just off the shelf, hosts the world's largest green turtle nesting populations, and Lizard Island and the Flinders group, two of the few high islands, have extensive fringing reefs. Most of the reef system is thought to have formed within the last 500,000 years, with the current phase of growth dating back perhaps 8,000 years. Diversity is highest in the north, where most of its 350 or so coral species occur. Spalding et al. (2001) put Australia's national reef area at about 48,960 km², and Souter et al. (2021) give 35,487 km² for the GCRMN subregion comprising the Torres Strait–northern GBR, central–southern GBR, and Tweed–Moreton ecoregions. The atlas notes that the park's zoning plan kept strictly protected areas within a much larger multiple-use framework, and Wilkinson (2006) notes that the 2004 rezoning divided the Marine Park into 70 bioregions, with the aim of placing at least 20% of each under no-take protection.

Souter et al. (2021) date the main recent losses on the GBR to the back-to-back bleaching of 2016 and 2017, which together affected its northern two-thirds; in 2016 alone, about 30% of shallow-water coral in the northern third died. Algal cover on the GBR almost doubled between 1996 and 2019, reaching 40.3% in 2018, the same year average coral cover hit its low of 24%. Cyclones and crown-of-thorns starfish added to the damage, with most of the reef exposed to severe cyclones over the two decades before the report. Earlier, Wilkinson (2006) reported a fourfold rise in the yearly load of sediments and nutrients reaching the GBR, and Souter et al. (2021) still count agricultural sediments, nutrients, and pesticides among the threats to reefs near the coast.

This unit brings together the 58 far northern Great Barrier Reef stations coded Pink in Anderson's 2014 survey set. The stations are the expedition's Pink stratum, reefs in the Preservation Zone, the Marine Park's strictest tier, where entry itself is restricted and nothing may be taken; on the zoning map two Ribbon Reef 6 positions (AUR608 and AUR610) fall about 70 to 80 m into the adjoining Buffer Zone. The stations run from about 11 to 15.4°S and were surveyed by in situ transect between 4 September and 2 October 2014; recorded station depths ran from 5.3 m at AU61A66 (the other expedition team's survey depth) to 24.7 m at AUPE127. They cover Unnamed Reefs 61A and 11-091, plus Carter, Hilder, Milman, Parkinson, Pearson, Williamson, and Yule Detached Reefs, along with Ribbon Reef 6.

On the backreef of Unnamed Reef 61A there is a maze of bommies, some over 30 m across, with at least 20 hard coral species on two transects (AU61A61) and, at AU61A63, a very large Pavona colony in Anderson's notes. His notes describe Pearson Reef's steep slope as highly rugose. Yule Detached Reef has walls falling past 50 m with coral still growing at 30 m. On the survey's second day Anderson called a leeward coral pinnacle on Ribbon Reef 6 (AUR611) "beautiful" and "interesting". On Unnamed Reef 11-091, a reef platform that looked scoured holds a steady 9-11 m for hundreds of meters under 2-3 knot currents (AU91111). In contrast, the Milman and Parkinson stations were silty, low-visibility reefs dominated by Goniopora, Alveopora, lettuce coral, and Pachyseris, where AUPS71 still held unbroken gold staghorn meadows in a couple of meters of water.

Protection status did not translate into uniform condition. Transect cover ranged from 3.4% at AUWL28 and 4.6% at AUWL26 on Williamson Reef to 75% at AU61A63. On one Williamson Reef dive (AUWL27) Anderson counted at least 22 crown-of-thorns starfish and believed they drove the loss; on a neighboring dive (AUWL25) he recorded 90-95% of the staghorn dead under sediment and cyanobacteria without assigning a cause. Crown-of-thorns starfish were also recorded on Pearson, Milman, and Parkinson Reefs. Hilder Reef had apparent recent storm rubble around 10 m. Pale, bleached, or dying needle coral (Seriatopora) was recorded across the majority of reefs in the zone, and photographs from AUCT53 and AUR607 show stark-white colonies beside pigmented neighbors. On Ribbon Reef 6 (AUR611), some mostly bleached Pocillopora were covered in mucus that Anderson noted looked exogenous rather than produced by the corals ("Very strange").