Researchers from the University of Western Australia wanted to find out exactly how genetically diverse the seagrass meadow in Shark Bay in Western Australia is. The results surprised the team, however, because during their investigation, they came across the largest plant in the world.
A vast seagrass carpet of the species Posidonia australis is 180 km long in the UNESCO World Heritage protected Shark Bay. In total, this “meadow” covers an area of 200 square kilometers. This carpet should be viewed as a plant, writes the team led by evolutionary biologist Elizabeth A. Sinclair from the University of Western Australia in the journal. Proceedings of the Royal Society B,
The study was actually planned to find plants that could be used to improve sea grass. “We are often asked how many different plants grow in seagrass beds, and this time we used genetic tools to answer that,” Sinclair says. Researchers were “blown away” by the results, says Jane Edgelow, who was involved in the study. Because all specimens were genetically identical, the giant carpet of sea grass is one plant. The large seagrass meadow is said to have emerged from a “colonization seedling” and spread back and forth over the years.
Not only does the plant set a size record, it is also unusual in other respects.
Because of its enormous size, researchers estimate the plant to be about 4,500 years old. In addition to the size record, the plant is also special because it is polyploid. This means that seaweed cells have more than two sets of chromosomes. This phenomenon occurs when two diploid parent plants – plants with two pairs of chromosomes in the cell nucleus – cross with each other. The newly formed seedling takes the entire genetic material from both the parents.
“Polyploid plants live in places with extreme environmental conditions and are often sterile, but they can continue to grow if they are not disturbed,” Sinclair says. So far, the plant has proven to be very resilient to the extreme environmental conditions in Shark Bay. “Even without successful flowering and seed production, the plant appears to be very resilient because it tolerates a wide range of temperature, salinity, and extreme light conditions. This will be a major stressor for most plants,” Sinclair says. Further studies are needed to reveal how seagrasses cope with current environmental conditions.
With its size, the giant sea meadow is far behind the world’s largest plant ever recorded. It is a cloned colony of 47,000 aspens in the state of Utah, USA called “Pando” which was discovered in 2018. Aspen nets are attached to the roots in the ground. Altogether, the “Pando” is 43 hectares in size and would therefore fit over 465 times the area of Australian sea grassland.