SYDNEY Researchers have made a startling discovery beneath the waters off Western Australia. A meadow of sea grass stretching more than 110 miles long was actually a single plant that had spent the past 4,500 years cloning itself to carpet an area three times larger than Manhattan.

The findings, published Wednesday in the Proceedings of the Royal Society B, make the colony of Posidonia australis, or ribbon weed, the largest known plant on Earth, scientists said.

Elizabeth Sinclair, a senior research fellow at the University of Western Australia and a lead author of the study, said her team has been testing seagrass meadows around Australia for genetic diversity for years to see how they respond to climate change. When her team visited an area known as Shark Bay, a relatively pristine landscape untouched by development, they went beneath the waves to collect samples of seagrass to see what types of plants were growing across the ocean floor.

The answer was one.

Its quite bizarre when you think about it, theres this plant in one end of the bay and then you move 100 kilometers down to the other end and its the same plant, Sinclair said.