The deep ocean, a realm of extreme pressure, darkness, and cold, has long been a mystery to us. It's a place where rare expeditions are often the only way to understand the life that exists there. But now, a new study using environmental DNA (eDNA) has opened a window into this hidden world off Western Australia's Nyinggulu coast, revealing a rich and surprising ecosystem that supports far more life than expected.
The Cape Range and Cloates submarine canyons, located about 1,200 kilometers north of Perth, were the focus of this expedition. A team led by Curtin University joined experts from several institutions to explore depths reaching over 4,500 meters aboard the Schmidt Ocean Institute's research vessel Falkor. They collected more than 1,000 samples, including 178 large water samples taken from multiple depths ranging from the surface to the seafloor.
These canyons connect shallow coastal waters to deep ocean basins and act as pathways that carry nutrients and organic matter downward, creating productive ecosystems that support diverse marine life. Instead of relying only on cameras or nets, scientists used eDNA to study genetic traces that animals leave behind in seawater.
One of the most striking discoveries was the presence of the giant squid, Architeuthis dux, whose DNA was detected in multiple samples across both deep-sea canyons. This species, which can grow over 10 meters long and weigh up to 275 kilograms, is rarely observed and had only two earlier records in the region.
The study identified more than 220 species across major animal groups, including jellyfish relatives, crustaceans, molluscs, fish, and echinoderms. Some groups, like cnidarians and arthropods, dominated the findings. In total, at least 83 species were flagged as new records or range extensions.
The canyons also revealed a wide range of unusual animals, including the faceless cusk eel, deep-sea cucumbers, acorn worms, and bioluminescent squid. Some species may even be new to science, with the DNA not matching existing records.
The research showed that life changes with depth, with each layer supporting different communities. The deepest waters often showed the highest overall biodiversity, with species like the pygmy sperm whale and Cuvier’s beaked whale also detected.
Environmental DNA allows scientists to detect fragile and fast-moving deep-sea species that traditional methods often miss. It can also capture a broader range of biodiversity, as seen in this study, where eDNA detected more groups of organisms than camera surveys alone.
The study's findings have significant implications for conservation. These ecosystems face threats from climate change, fishing, mining, and pollution, and some impacts, like bottom trawling, can reduce biodiversity and damage habitats for decades. Understanding what lives in the deep ocean is essential for informed management and conservation.
Better knowledge of deep-sea biodiversity can shape marine policies, helping to plan marine parks and assess environmental impacts. By combining eDNA with conventional deep-sea survey techniques, we can build a far more complete picture of biodiversity, revealing species, ecosystems, and ecological patterns that would otherwise remain hidden.
This study, published in the journal Environmental DNA, highlights the potential of eDNA to revolutionize our understanding of the deep ocean and guide future decisions to protect these unseen ecosystems.
