Elizabeth Sinclair– Senior Research Fellow, The University of Western Australia.
Gary Kendrick– Winthrop Professor, Oceans Institute, The University of Western Australia.
Jane Edgeloe– PhD prospect (Marine Biology), The University of Western Australia.
Martin Breed– Senior Lecturer in Biology, Flinders University.
These underwater seagrass meadows grow in two ways: by sexual reproduction, which assists them generate new gene combinations and hereditary variety, and likewise by extending their rhizomes, the underground stems from which shoots and roots emerge.
To learn how many different private plants are growing in a seagrass meadow, you have to evaluate their DNA. We did this for meadows of ribbon weed seagrass called Posidonia australis in the shallow sun-drenched waters of the Shark Bay World Heritage Area, in Western Australia.
The result blew us away: it was all one plant. One single plant has actually broadened over a stretch of 180 km (112 miles) making it the largest known plant on Earth.
We collected shoot samples from ten seagrass meadows from throughout Shark Bay, in waters where the salt levels vary from typical ocean salinity to practically twice as salty. In all samples, we studied 18,000 genetic markers to show that 200 km ²( 77 miles ²) of ribbon weed meadows broadened from a single, colonizing seedling.
Sampling Posidonia. Credit: Rachel Austin
How did it progress?
What makes this seagrass plant special from others, other than its massive size, is that it has twice as many chromosomes as its relatives. This makes it what scientists call a “polyploid.”.
Most of the time, a seagrass seedling will inherit half the genome of each of its moms and dads. Polyploids, nevertheless, bring the entire genome of each of their parents.
There are lots of polyploid plant species, such as potatoes, canola, and bananas. In nature, they typically reside in places with extreme environmental conditions.
Polyploids are typically sterilized, but can continue to grow indefinitely if left undisturbed. This seagrass has done simply that.
How old is this plant?
The sandy dunes of Shark Bay flooded some 8,500 years ago, when the water level rose after the last glacial epoch. Over the following centuries, the expanding seagrass meadows made shallow seaside banks and sills through creating and catching sediment, which made the water saltier.
There is also a great deal of light in the waters of Shark Bay, along with low levels of nutrients and large temperature changes. Regardless of this hostile environment, the plant has actually been able to adjust and thrive.
The shallow, salted waters of Shark Bay. Credit: Angela Rossen.
It is challenging to identify the exact age of a seagrass meadow, but we estimate the Shark Bay plant is around 4,500 years of ages, based upon its size and growth rate.
Other big plants have actually been reported in both marine and land systems, such as a 6,000-tonne trembling aspen in Utah, however this seagrass seems the largest to date.
Other big seagrass plants have also been found, consisting of a carefully related Mediterranean seagrass called Posidonia oceanica, which covers more than 15 km (9 miles) and may be around 100,000 years old.
Why does this matter?
In the summertime of 2010– 11, a serious heatwave struck land and sea ecosystems along the Western Australian shoreline.
Shark Bays seagrass meadows suffered extensive damage in the heatwave. The ribbon weed meadows have actually begun to recover.
This is somewhat unexpected, as this seagrass does not appear to recreate sexually– which would typically be the finest way to adapt to changing conditions.
We have observed seagrass flowers in the Shark Bay meadows, which suggests the seagrass are sexually active, however their fruits (the outcome of successful seagrass sex) are hardly ever seen.
Flowers emerging from Posidonia australis seagrass. Credit: Angela Rossen.
Our single plant may in fact be sterilized. This makes its success in the variable waters of Shark Bay rather a conundrum: plants that do not have sex tend to likewise have low levels of hereditary diversity, which must lower their capability to deal with changing environments.
However, we suspect that our seagrass in Shark Bay has genes that are exceptionally appropriate to its regional, however variable environment, and perhaps that is why it does not require to make love to be successful.
Even without successful blooming and seed production, the giant plant seems very resilient. It experiences a broad variety of water temperature levels (from 17ºC/ 63ºF to 30ºC/ 86ºF in some years) and salt levels.
Despite these variable conditions and the high light levels (which are generally demanding for seagrass), the plant can keep its physiological processes and prosper. So how does it cope?
We assume that this plant has a small number of somatic anomalies (small genetic modifications that are not handed down to offspring) across its 180 km (112 mile) variety that assist it continue under local conditions.
However, this is simply a hunch and we are tackling this hypothesis experimentally. We have actually established a series of experiments in Shark Bay to really understand how the plant makes it through and flourishes under such variable conditions.
Transplant experiments. Credit: Martin Breed.
The future of seagrass.
Seagrasses safeguard our coasts from storm damage, shop big amounts of carbon, and provide an environment for a great diversity of wildlife. Conserving and also bring back seagrass meadows has a vital role in climate modification mitigation and adjustment.
Seagrasses are not immune from climate change effects: warming temperature levels, ocean acidification, and extreme weather events are substantial obstacles for them.
The comprehensive picture we now have of the great strength of the giant seagrass of Shark Bay offers us with the hope they will be around for many years to come, especially if major action is taken on climate modification.
Composed by:.
Ribbon weed, Posidonia australis, meadow in Shark Bay, Western Australia Credit: Rachel Austin, University of Western Australia.
Scientists were examining meadows of ribbon weed seagrass utilizing DNA analysis. The stunning results blew them away; the 18,000 DNA markers they analyzed in Shark Bay World Heritage Area, in Western Australia revealed a single plant expanded to stretch 112 miles. This makes it the worlds largest known plant.
In some way this single seedling grew to cover an area of 77 square miles, extending through waters that are rather different in temperature and salinity. Based on its size and growth rate, the researchers approximate that it is 4,500 years of ages.
Next time you go diving or snorkeling, have a close take a look at those wondrously long, brilliant green ribbons, waving with the ups and downs of water. They are seagrasses– marine plants which produce flowers, fruit, and seedlings each year, like their land-based relatives.
This article was very first published in The Conversation.
