The sprawling seagrass, a marine flowering plant known as Posidonia australis, stretches for more than 180 kilometers in Shark Bay, a wilderness area protected as a World Heritage Site, said researcher Elizabeth Sinclair. principal at the School of Biology. University of Western Australia Institute of Science and Oceans.
That’s roughly the distance between San Diego and Los Angeles.
The plant is so tall because it clones itself, creating genetically identical offshoots. This process is a rare mode of reproduction in the animal kingdom although it does occur under certain environmental conditions and occurs more often in certain plants, fungi, and bacteria.
“The answer definitely surprised us – just ONE! That’s it, a single factory stretched 180 km in Shark Bay, making it the largest known factory on Earth,” she said per E-mail.
Sinclair and his colleagues collected samples from 10 locations within the Shark Bay seagrass prairie range in 2012 and 2019. The research team also measured environmental conditions including depth, temperature water and salinity.
“We’ve been studying cold-water seagrasses in southern Australia for some time, to understand how genetically diverse they are and how connected the grasslands are,” Sinclair said.
The scientists were able to sequence the DNA of the seagrass samples, which revealed that it was a single plant.
“The plant was able to continue to grow through vegetative growth—spreading its rhizomes (root stems) outward—like buffalo grass would in your back garden, spreading the runners outward. The only difference is that the seagrass rhizomes are under a sandy seabed so you can’t see them, just the shoots in the water column,” she said.
“What was even more interesting is that it has double the number of chromosomes than in other populations we had studied. It has 40, not the usual 20,” she added.
Seagrasses inhabit sea coasts and estuaries around the world.
The study suggested that reproduction by cloning helped the herbarium to adapt to habitat conditions which were more extreme than where seagrasses are usually found – saltier water, high light levels and large temperature fluctuations.
“Individual seagrass clones can persist almost indefinitely if left undisturbed, because they rely on vegetative and horizontal expansion of rhizomes, rather than sexual reproduction,” Sinclair said.