N. GBR - Green (AUSD129)

Setting

Station AUSD129 on Siddons Reef lies in a Marine National Park (Green) Zone. The expedition's own site table classifies AUSD129 as a sheltered mid shelf reef on an intermediate aspect.

General benthic features

Siddons Reef's first dive stop opens onto a level Acropora meadow at 10 m, anchored in shallower water at 7 m — an easy survey target that nonetheless kept divers from reaching much past 12 m within a reasonable swim. Alongside the hard coral already reported for this site, the same transects recorded 2.6% crustose coralline algae, 17% turf, 7.5% macroalgae, and 0.5% cyanobacteria. Non-living substrate came to 6.9% dead coral, 15% rubble, and 2.5% sand. These figures come from the expedition's own 933-site benthic master and are survey results, not photographic estimates.

Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• The GRE survey transects recorded 52% coral cover at 6.3 m; Anderson's own transects at 9-11 m ran 15-70% by eye, and the richly diverse 5 m shallows held staghorn thickets mixed with massive Porites, Lobophyllia, and multiple Pocillopora-relatives.
• Transect mean 52 ± 4.4% SE (n = 8 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

Not everything here was thriving, though — needle coral (Seriatopora hystrix) was dying in more than one spot, and one dense staghorn thicket had lost roughly half its colonies to death and algae overgrowth.

Fish and other fauna

A real highlight of the dive: Anderson photographed benthic ctenophores for the first time in his life, while whitetip and gray reef sharks cruised the reef. Paired fish transects recorded about 41 fish species per transect and about 20 kg per 100 m2 of biomass.

Comparisons with other data

No prior survey data from this site. If you would like to share yours, please email us.