N. GBR - Green (AUSD131)

Setting

Siddons Reef's second dive of the day repeats the broad, level Acropora-meadow terrain of the first — a 10-11 m expanse stretching for hundreds of meters, with strangely no Pocillopora in the shallows — until a tide change partway through kicked up a strong current. The expedition's own site table classifies AUSD131 as a sheltered mid shelf reef on an exposed aspect.

General benthic features

Alongside the hard coral already reported for this site, the same transects recorded 19% crustose coralline algae, 11% turf, and 1.5% cyanobacteria. Non-living substrate came to 10% dead coral, 32% rubble, and 2.2% 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 53% coral cover; Anderson's own six transects at 10.7-11 m ran 10-25% live coral by eye, amid Favites, Lobophyllia, a huge Turbinaria colony, and heavy turf algae and cyanobacteria in places.
• Transect mean 50 ± 3.3% 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

A single crown-of-thorns starfish turned up here. The dive's clearest and most repeated signal, though, was needle coral (Seriatopora hystrix) in poor shape: sickly or dying S. hystrix colonies showed up on five of six transects, and one stretch of dead, algae-covered staghorn thicket opened the dive.

Fish and other fauna

Several whitetip and gray reef sharks were logged. Paired fish transects recorded about 32 fish species per transect and about 9.2 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.