World's biggest plant discovered off Australian coast

In a study published on Wednesday, researchers from Flinders University in South Australia (SA) and the University of Western Australia (UWA) revealed they have discovered a seagrass stretching 180 km in Western Australia's Shark Bay.

The researchers sought to understand the diversity of seagrass meadows in Shark Bay using genetic tools and were surprised to discover it was one vast organism of the Posidonia australis species.

They estimate that it is at least 4,500 years old.

Martin Breed, an ecologist from Flinders University and co-author of the study, said the team was bewildered about how the plant is continuing to thrive.

"This single plant may in fact be sterile; it doesn't have sex. How it's survived and thrived for so long is really puzzling. Plants that don't have sex tend to also have reduced genetic diversity, which they normally need when dealing with environmental change," he said in a media release.

"Our seagrass has seen its fair share of environmental change too. Even today, it experiences a huge range of average temperatures; from 17 to 30 degrees Celsius. Salinities from normal seawater to double that. And from darkness to extreme high light conditions. These conditions would typically be highly stressful for plants. Yet, it appears to keep on going."

After conducting further tests, researchers found that the plant is a polyploid, meaning it has twice as many chromosomes as its relatives, and it will continue to grow if left undisturbed.

The team has set up further tests to better understand how the ancient plant survives in such variable conditions.