Seamounts, Canyons & Reefs of the Coral Sea

From Modelling to Diving with SuBastian

Dr Zhi Huang, Geoscience Australia
Aug. 15 2020

For a first-timer going on a marine survey, this voyage on RV Falkor in the Coral Sea Marine Park is a dream come true. Importantly, as a marine environmental modeller, this voyage is giving me first-hand experience of data acquisition and a much better understanding of the strengths and limitations of data that is acquired at sea. For me, life on board Falkor is full of excitement and anticipation as we map and sample a huge variety of habitats. As well as processing and analysing the acoustic data we are collecting, I also get to watch the spectacular sunrises at sea! My name is Zhi Huang, a marine environmental modeller at Geoscience Australia.

For Dr Zhi Huang, Geoscience Australia, this is his first time on a multi-day expedition at sea. Zhi is an expert at compiling the data that is collected from all the instruments on board ships like the Falkor, and to see these operations first hand is an unforgettable and valuable experience that will help him better understand and interpret oceanographic data sets.Dean Miller / SOI

Today, I would like to share with you what we observed at Cairns Seamount, which is the second study site on this cruise. Cairns Seamount, is a “shallow water” seamount which rises from a depth of around 1,200 m up to 60 m. It is located 150 km east of Cairns, in a very large depression in the seabed call the Queensland Trough. Although Cairns Seamount is a popular fishing destination, scientific knowledge of the seamount is limited. We have acquired a range of scientific data of the seamount using state-of-the-art instruments, including multibeam eco-sounders, ROV SuBastian, and AUV Sirius. Our objectives are to shed some light on the origin of the seamount, the biological organisms living on and around it, and its oceanographic characteristics.

High Resolution Image from an AUV Sirius transect showing coral and seafloor.AUV Sirius

We have topographically mapped Cairns Seamount in unprecedented detail using Falkor’s multibeam eco-sounders. The seamount is conical in shape and relatively small – its base covers 8.2 km2 and the flat top 0.2 km2. The bathymetry and sediment, rock and biological samples, coupled with high-resolution images acquired by the ROV and AUV, will enable us to characterise the biodiversity on and around the seamount and provide insights into the process influencing these spatial patterns.

The Benthic community on Cairns Seamount includes corals, sponges, fish, and crustaceans.ROV SuBastian / SOI

The new high-resolution video footage and still images reveal a range of benthic species. We observed many animals in the water column, including fish and jellyfish, sustained by very small food particles (“marine snow”). These particles also sustain deep-water corals and other benthic suspension feeders that have colonised the seabed, often on hard rocks within predominant deep sandy areas. As the ROV ascended up the seamount flank, we observed major changes in benthic communities and relatively barren areas of exposed hard rock, with occasional stony and soft corals and sea urchins at mid-water depths (400-600 m). The abundance and diversity of species increased dramatically in the shallow-water section of the seamount (<200 m depth), where sunlight reaches the seabed. Various coral species, sponges, crustose coralline algae and reef fish were observed in this mesophotic environment. Cairns Seamount is clearly a distinctive structure in the western Coral Sea that supports a relatively high degree of biodiversity and an important feature of the Coral Sea Marine Park.

Data collected from the various instruments on Falkor, ROV SuBastian, and AUV Sirius allow scientists to create high detailed 3D images for the first time to show us exactly what the Cairns Seamount looks like in terms of its geological structure.Dr Zhi Huang, Geoscience Australia

Share This