Researchers documented 29,556 individual organisms in video footage taken by crewed submersible dives to three underwater trenches off the coast of Japan.
“This provided one of the most detailed observations of seafloor biodiversity and habitats at these depths,” says Dr Denise Swanborn, from The University of Western Australia’s School of Biological Sciences and Minderoo-UWA Deep-Sea Research Centre. “We found differences in community composition and diversity between trenches, linked to depth and nutrient input from surface waters.”
The subs visited three sites – the Japan, Ryukyu and Izu-Ogasawara trenches – between 6,939 metres and 9,775 metres deep. They found that each one had its own interesting make up of animals living there.
“Within trenches, at the same depth band, differences in historical seismic disturbance and seafloor stability created different communities,” says Swanborn.
The Japan Trench had lots of sea cucumbers living in its nutrient-rich waters while the Ryukyu Trench, which has less food available, had almost no sea cucumbers but lots of brittle stars. Meanwhile, the Izu-Ogasawara Trench was home to thriving meadows of sea lilies (crinoids).
Their findings are published in the Journal of Biogeography.
Image and video credit: University of Western Australia, Caladan Oceanic LLC and Inkfish LLC
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