A Very Big Plant, Very Old, and Very Important Too
Posidonia australis, seagrass meadow (credit: U-WA)
Posidonia australis is likely a plant that few people have ever heard of before. The Ribbon Weed plant is worth getting to know better as it is a truely unique.
Posidonia is a flowering plant, produces seeds, that grows in shallow seawater around the southern coasts of Australia. It was named for the Greek god that ruled the oceans, Poseidon. Researchers from the University of Western Australia, studying the underwater seagrass meadow near Sharks Bay, determined that it is vast in scale, over 75 square miles (49,000 acres), but also a solo plant, having been established by single seed, and likely 4500 years ancient.
These features may have resulted from the Ribbon polyploidy, the genetic doubling of the number of chromosomes, that allowed it to grow to such an enormous size, durability, and age. It is also is remarkably hardy growing in locations across Sharks Bay that have variable environmental conditions. Likely, This is likely a result of it genetic polypoidy as well. Commenting on their genetic discoveries one of the researchers, Elizabeth Sinclair, noted the seagrass:
"appears to be really resilient, experiencing a wide range of temperatures and salinities plus extreme high light conditions, which together would typically be highly stressful for most plants."
This Ribbon Weed meadow therefore consists of the largest single plant anywhere, land or sea, and is one of the oldest living organisms on Earth.
Not only is the newly discovered seagrass plant huge and old, such meadows provide major ecosystem services wherever they occur. They habitat, shelter, and food to many sea creatures protecting endangered seahorses, penguins, seadragons, and turtles which utilize them in myriad ways. They are also nurseries and feeding grounds for young fry of commercial and recreational fish, while improving water quality by filtering, removing, and recycling nutrients. Likewise, the plant's root systems stabilize sediment on the seafloor that helps to protect coastal zones during storms. Recent discoveries show that carbon dioxide absorbed during photosynthesis is faster than rate of tropical rainforests from their rapid grow rates. These underwater grasses may account for 10% of the ocean's capacity to capture heat-trapping, atmospheric, carbon dioxide while building their meadows of leaves and roots.
Posidonia is not only very big, very old, but also very powerful not unlike the Greek sea-god they well respected! WHB