Deep-sea researchers exploring underwater canyons off the coast of Nyinggulu (Ningaloo), Western Australia, have discovered hundreds of species, including many rare creatures.
The scientists didn't need to see the marine animals to know they are living in Australia's deep waters – instead, they detected their presence through water samples.
As animals live out their lives, they shed tiny DNA particles through skin, mucus and faeces. Researchers can figure out what swam by recently by collecting small seawater samples and analysing them to detect these tiny traces (known as environmental DNA, or eDNA).
The scientists conducted surveys of the deep-sea Cape Range and Cloates canyons, which are located around 1,200km north of Perth, to try to find out more about the region’s hidden biodiversity. They collected many different samples, some even as deep as 4,510m.
The findings were published recently in the journal Environmental DNA.
"These canyons are incredibly rich ecosystems and, until now, they’ve been largely unexplored because of the difficulty of working at such extreme depths," said the study’s lead author Georgia Nester. Nester is now a researcher at the University of Western Australia but was a PhD candidate at Curtin University at the time.
"With eDNA, a single water sample can tell us about hundreds of species at once. That means we can dramatically expand our understanding of deep-water environments in a way that simply hasn’t been possible before," she adds.
The eDNA results helped them to paint a picture of life far below the waves, even when they didn’t directly observe many of the elusive species. Perhaps one of the biggest surprises was the presence of a giant squid, a rarely seen deep-sea cephalopod that has not been recorded in Western Australian waters for more than 25 years.
"This is the first record of a giant squid detected off Western Australia’s coast using eDNA protocols and the northernmost record of [the species] A. dux in the eastern Indian Ocean,” says Dr Lisa Kirkendale, WA Museum Head of Aquatic Zoology and Curator of Molluscs.
Thanks to their extensive tentacles, giant squid can grow to more than 13m long and have eyes the size of dinner plates. Yet, these ocean behemoths are rarely seen because they live hundreds of metres below the surface.
“Finding evidence of a giant squid really captures people’s imagination, but it’s just one part of a much bigger picture,” says Nester.
The researchers found evidence of 226 species in the deep waters around the canyons. These included pygmy sperm whales – which release a cloud of intestinal fluid like a squid’s ink when under threat to distract predators while they escape – and the world’s deepest diving mammals, Cuvier’s beaked whales. They also recorded the wonderfully named bony-eared assfish.
Some animals had never been detected in Western Australian waters before, such as sleeper sharks, slender snaggletooths and faceless cusk eels. Other species might be new. “We found a large number of species that don’t neatly match anything currently recorded, which doesn’t automatically mean they’re new to science, but it strongly suggests there is a vast amount of deep-sea biodiversity we’re only just beginning to uncover,” adds Nester.
Discovering how many creatures are thriving in these deep-sea habitats plays an important part in informing protection measures.
“Deep-sea ecosystems are vast, remote and expensive to study, yet they face growing pressure from climate change, fishing and resource extraction,” says senior author Zoe Richards, associate professor at Curtin’s School of Molecular and Life Sciences.
“Environmental DNA gives us a scalable, non-invasive way to build baseline knowledge of what lives there, which is essential for informed management and conservation,” she adds. “You can’t protect what you don’t know exists.”
In Pictures: life in Western Australia's deep-sea canyons
These images, captured by Schmidt Ocean Institute researchers, reveal the vast array of life in Western Australia's deep-sea canyons.
Images and video credit: Schmidt Ocean Institute | Attribution-NonCommercial-ShareAlike CC BY-NC-SA Attribution
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