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Deep-sea discoveries by WA museum

Charitha Pattiaratchi, Professor of Coastal Oceanography at University of Western Australia and Malcolm McCullock, Professor, University of WA, We are finally learning the Perth Canyon’s deep-sea secrets, The Conversation, 10 March 2015.

Skeleton of deep-sea coral. Photo credit:SOI/Paolo Montagna & Marco Taviani.

After going unexplored for centuries, one of Australia’s biggest marine features is finally giving up its secrets. The Perth Canyon, roughly the length of the Grand Canyon, twice as deep and reaching depths of 4000 metres below the waves, is just 20 kilometres west of Rottnest Island, yet it has never been properly surveyed – until now.

Despite being so close to Perth and Fremantle, little is known about life in this abyss. But an ocean expedition currently exploring the canyon is to change that.

Well fathomed, but a mystery

Submarine canyons are global biodiversity hotspots with high biomass and biological productivity – and the 220km-long Perth Canyon is no exception. From the canyon’s head, in waters just 50m deep, to where its mouth opens out onto the abyssal plain 4000m down, it is thought that many species cling to its 70-degree sloping walls.

The canyon, an extension of the Swan River system, was formed over tens of millions of years. It is the main biodiversity hotspot between Ningaloo Reef and Kangaroo Island, and marks the southern boundary for many tropical species groups. Deep ocean currents upwelling in the canyon create a cold-water, nutrient-rich oasis under the warm waters of the Leeuwin current, attracting blue whales and other large animals that migrate to the canyon seasonally to feed.

The Australian government has proposed that the canyon be declared a marine park.

A team of scientists from the University of Western Australia, together with researchers from the Western Australian Museum, CSIRO and the Institute of Marine Sciences in Italy, are spending 12 days investigating the Perth Canyon on board the R/V Falkor, a research vessel run by the Schmidt Ocean Institut.

Using state-of-the-art mapping systems and a remotely operated vehicle to examine the life in the canyon, the cruise’s main goal is to examine and collect a variety of marine organisms that are living at great depths, particularly deep-sea corals. These corals, like their shallow-water counterparts, form reef structures that create local biodiversity hotspots by attracting a range of other animals.

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