Scientists Find Seagrass That May Be the Oldest Living Organism on Earth

Ancient patches of a giant seagrass in the Mediterranean Sea are now considered the oldest living organism on Earth after scientists dated them as up to 200,000 years old.

A meadow of the seagrass plant Posidonia oceanica, which spreads by creating clones of itself. Photo: Alessio Di Lorenzo/Flickr

The world’s oldest living organism may not be that 43,000 year-old Tasmanian plant after all.

Scientists have discovered giant patches of seagrass in the Mediterranean Sea that are thought to be up to 200,000-years-old, The Huff Post reports.

Seagrass meadows can be composed of ancient giant clones, organisms stretching up to nearly 10 miles wide that could be more than 100,000 years old.

Australian scientists sequenced the DNA of samples of the giant seagrass, Posidonia oceanic, from 40 underwater meadows in an area spanning more than 2,000 miles, from Spain to Cyprus, according to The Telegraph.

The study, published in the journal PLoS One, showed the organisms ranged from 12,000 years to 200,000-years-old, with most of them likely being around 100,000-years-old.

Prof Carlos Duarte, from the University of Western Australia, said the seagrass has been able to reach such old age because it can reproduce asexually and generate clones of itself. Organisms that can only reproduce sexually are inevitably lost at each generation, he added.

“They are continually producing new branches,” he told The Daily Telegraph. “They spread very slowly and cover a very large area giving them more area to mine resources. They can then store nutrients within their very large branches during bad conditions for growth.”

“Clonal organisms have this extraordinary capacity that when a ‘perfect’ genome emerges, it can be transmitted through generations without being altered, and has potentially no end,” said researcher Sophie Arnaud-Haond, a marine biologist at the French Research Institute for Exploration of the Sea, according to MSNBC.

To learn more about how long the seagrass P. oceanica can actually live, researchers analyzed 40 meadows of it across 2,175 miles (3,500 kilometers) of the Mediterranean.

Not all of the seagrass the scientists discovered was genetically identical. However, the seagrass clones they did find suggest both extreme size and age. Some reached up to 9.3 miles (15 kilometers) wide and may well be more than 100,000 years old.

Prof Duarte said that while the seagrass is one of the world’s most resilient organisms, it has begun to decline due to coastal development and global warming. “If climate change continues, the outlook for this species is very bad,” he said.

“The seagrass in the Mediterranean is already in clear decline due to shoreline construction and declining water quality and this decline has been exacerbated by climate change. As the water warms, the organisms move slowly to higher altitudes. The Mediterranean is locked to the north by the European continent.

“They cannot move. The outlook is very bad.”

Seagrasses are the foundation of key coastal ecosystems but have waned globally for the past 20 years, with P. oceanica meadows declining at an estimated rate of about 5 percent annually.

“Posidonia oceanica’s clones have been able to survive greatly fluctuating environmental conditions, and meadows we observe nowadays are the outcome of millennia of evolution,” Arnaud-Haond said.

“On the one hand, this suggests an ability to cope with environmental change that could be a positive clue on their ability to cope with medium- and long-term prospects of global change.”

On the other hand, changes are occurring nowadays at an unprecedented rate, and the sharp decline of seagrass meadows in general and Posidonia oceanica in particular is raising concerns as to the ability of this slow-growing species and its old, patiently selected clones to face these new and rapidly occurring environmental challenges.”

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