Jun 5, 2022 - Science

The world's largest known plant discovered off Australian coast

Alison Snyder

Shark Bay seagrass, Posidonia australis. Photo: Rachel Austin/UWA — Shark Bay seagrass, *Posidonia australis.* Photo: Rachel Austin/UWA

A seagrass meadow spanning more than 111 miles in western Australia is a single plant — and the world's largest known organism, according to a study published this week.

The big picture: "Nature is amazing if you don't disturb it," says Elizabeth Sinclair, an evolutionary biologist at the University of Western Australia and a co-author of the study published in the Proceedings of the Royal Society B.

Details: DNA analysis revealed the meadow in Shark Bay was a single plant made from clones that grow from rhizomes, a type of stem that extends in the sand in multiple directions.

It takes up about 77 square miles and the researchers estimate it is 4,500 years old.

The intrigue: Normally, seagrass (P. australis) commonly found in the region has 20 chromosomes, but the large clone has 40 chromosomes.

"That effectively doubles the amount of [genetic] variation," Sinclair says. "Having all this extra variation likely gives it an advantage to coping with a wider range in environments, including the large change in salinity, or saltiness, of the water."

What's next: The team is now looking at how different pieces of the plant can live in different local environments with varying amounts of salt, Sinclair says.

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The world's largest known plant discovered off Australian coast

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