Diamantina Fracture Zone & Perth Canyon
The Journey
In March 2022 the Minderoo-UWA Deep-Sea Research Centre embarked on a 14-day voyage aboard the Pangaea Ocean Explorer to explore the abyssal and hadal depths of the Diamantina Fracture Zone and Perth Canyon in the Southeast Indian Ocean.
The cruise was led by centre director Professor Alan Jamieson who was accompanied by UWA fellows Dr Todd Bond and Dr Prema Arasu. They were joined by PhD researcher Jürgen Valckenaere from the UWA Wernberg Lab and OceanOmics research assistant Marcelle Ayad.
The Diamantina Fracture Zone is a 3400 km-wide area of ocean trenches and ridges which were formed as the Australian and Antarctic continents separated. The deepest part is the Dortdrecht Deep 1400km west of Fremantle at over 7000m. Perth Canyon is 19km west of Rottnest Island and reaches depths of 5000m.
Equipment
Three full ocean depth-rated landers were designed, constructed and used for the first time on this voyage. Each one was equipped with a baited HD video camera, currentmeter and CTD-O2 instrument, a baited amphipod trap, and bottom water samplers. The cameras are filming continuously from their deployment to their retrieval, as seen in this video.
A total of 19 lander deployments were conducted over the duration of the cruise: 16 at Diamantina and 3 at Perth Canyon, yielding >130 hours of video footage, hundreds of amphipods for genomic analysis, and two likely new species of snailfish.
Squid
The landers' descent is a passive process, controlled by a heavy ballast attached to the underside. Depending on the depth of the deployment area, a descent can take 2-4 hours. As the cameras are filming continuously, there is always a chance of spotting interesting animals in the midwater.
Snailfish and Cusk Eels
The snailfish was caught within the easternmost part of the of the Diamantina Fracture Zone at 6177m deep. It is shown here (purple) with two larger cusk eels (Ophidiidae sp.) An adult and juvenile were caught with a yabby trap attached to the lander.
Snailfish are a family of bony fishes whose distribution ranges from intertidal zones to hadal depths. The hadal species feed on amphipods which are attracted to the baited arms and fish traps on the lander.
Deep-Sea Jellies
This trachymedusae (deep sea jellyfish) likely belongs to the Crossota genus. This one was filmed at a depth of approximately 4000m within the Diamantina Fracture Zone.
The trachymedusae are an order of Cnidaria known to inhabit abyssal and hadal depths. Their size ranges from 0.5 to 5cm in diameter.
Deep-Sea Cucumber
This deep-sea cucumber (Enypniastes eximia) is also known as the headless chicken monster due to its strange appearance. Although they are largely benthic, these ones have evolved fins which allow them to swim above the sea floor in search for food.
Visible on the sea floor are several deep-sea crabs with symbiotic anemone visible on their carapaces.
Cape Leeuwin Manganese Nodule Field
Manganese nodules are rock-shaped ore of valuable metals including copper, nickel, and cobalt. They occur at abyssal and hadal depths and take millions of years to form. Nodule fields are a unique habitat host to a variety of deep sea animals specialised to living in the sediment and on the nodules.
However, these fields are targeted by the deep-sea mining industry as the metals within these nodules are used in batteries, electric vehicles and solar panels. Such extractive processes will result in habitat destruction and the loss of the species that live there.