Posidonia australis

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Posidonia australis
Posidonia australis Spencers Gulf.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
Family: Posidoniaceae
Genus: Posidonia
Species:
P. australis
Binomial name
Posidonia australis

Posidonia australis, also known as fibre-ball weed or ribbon weed, is a species of seagrass that occurs in the southern waters of Australia. It forms large meadows important to environmental conservation. Balls of decomposing detritus from the foliage are found along nearby shore-lines.

Contents

In 2022, a single stand in Shark Bay was reported by scientists to not only be the largest plant in the world, but the largest organism by square size. [2]

Description

From left: immature fruits attached to plant, mature fruit released from plant, splitting fruit ready to release seed. Posidonia australis fruits and seed.jpg
From left: immature fruits attached to plant, mature fruit released from plant, splitting fruit ready to release seed.

Posidonia australis is a flowering plant occurring in dense meadows, or along channels, in white sand. It is found at depths from 1–15 m (3–49 ft). Subsurface rhizomes and roots provide stability in the sands it occupies. Erect rhizomes and leaves reduce the accumulation of silt.

The leaves are ribbon-like and 11–20 mm (0.43–0.79 in) wide. They are bright green, perhaps becoming browned with age. [3] The terminus of the leaf is rounded or absent through damage. They are arranged in groups with older leaves on the outside, longer and differing in form from the younger leaves they surround.

The species is monoecious. The flowers appear on small spikes on leafless stems, two bracts on each spike. The plant pollinates by hydrophily, by dispersing in the water. [4]

Posidonia australis reproduction usually occurs through sexual or asexual methods but, under extreme conditions, by pseudovivipary. [5]

A 2013 study showed that P. australis can sequester carbon 35 times more efficiently than rainforests. [6]

In 2022, a study by the School of Biological Sciences and Oceans Institute at The University of Western Australia showed that a single plant of this species can grow vegetatively by using rhizomes to cover an extensive area, similar to buffalo grass. This particular specimen has double the number of chromosomes of other studied populations (40 chromosomes instead of the usual 20). [7]

Distribution

Detrital P. australis accumulation at West Beach, South Australia West Beach wrack.JPG
Detrital P. australis accumulation at West Beach, South Australia

This species is found in waters around the southern coast of Australia. In Western Australia it occurs in the Shark Bay region, around islands of the Houtman Abrolhos, and southward along the coast of the Swan Coastal Plain. The species is recorded at the edge of the Esperance Plains, the Archipelago of the Recherche, at the southern coast of the southwest region. The range extends to the east to coastal areas of New South Wales, South Australia, Tasmania, and Victoria. [4]

A sign of a nearby occurrence of Posidonia is the presence of masses of decomposing leaves on beaches, forming fibrous balls.

Largest known organism

A research article in the Proceedings of the Royal Society [8] reported in June 2022 that genetic testing had revealed that samples of Posidonia australis taken from a meadow in Shark Bay up to 180 km (110 miles) apart were all from a single clone of the same plant. The plant covers an area of seafloor of around 200 km2 (49,000 acres). [9] This would make it the largest known organism in the world by area, exceeding the size of a colony of the Armillaria ostoyae fungus in Malheur National Forest, Oregon that extends 9.1 km2 (2,000 acres), as well as a stand of quaking aspen trees in Utah that extends over more than 40 ha (100 acres). [9]

The plant is estimated to have taken at least 4,500 years [8] to grow to this size by using rhizomes to colonise new parts of the seafloor, assuming a rhizome growth rate of around 35 cm (14 in) a year. [10] [9] This age puts it among the oldest known clonal plants too.

Taxonomy

This species is a member of the family Posidoniaceae, one of eight occurring in Australia. The ninth member, Posidonia oceanica , is found in the Mediterranean sea. The genus name for this species, Posidonia, is given for the god of the seas Poseidon, and australis refers to the southern distribution.

The species was first described by Joseph Hooker in Flora Tasmaniae . [11] Common names for the plant include fibre-ball weed and ribbon weed. [9]

Conservation status

IUCN lists this species as "near threatened", [1] while the meadows in New South Wales have been listed by the Commonwealth of Australia as an endangered ecological community since 2015. [12]

Related Research Articles

<span class="mw-page-title-main">Seagrass</span> Plants that grow in marine environments

Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families, all in the order Alismatales. Seagrasses evolved from terrestrial plants which recolonised the ocean 70 to 100 million years ago.

<span class="mw-page-title-main">Shark Bay</span> Bay of the Indian Ocean in Western Australia

Shark Bay is a World Heritage Site in the Gascoyne region of Western Australia. The 23,000-square-kilometre (8,900 sq mi) area is located approximately 800 kilometres (500 mi) north of Perth, on the westernmost point of the Australian continent. UNESCO's listing of Shark Bay as a World Heritage Site reads:

<i>Zostera</i> Genus of aquatic plants

Zostera is a small genus of widely distributed seagrasses, commonly called marine eelgrass, or simply seagrass or eelgrass, and also known as seaweed by some fishermen and recreational boaters including yachtsmen. The genus Zostera contains 15 species.

<span class="mw-page-title-main">Seagrass meadow</span> Underwater ecosystem

A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and long green, grass-like leaves. They produce seeds and pollen and have roots and rhizomes which anchor them in seafloor sand.

<i>Amphibolis griffithii</i> Species of plant

Amphibolis griffithii is a seagrass found in waters along the southwestern coasts of Western Australia, extending to Encounter Bay in South Australia.

Amphibolis antarctica is a species of flowering plant in the family Cymodoceaceae. It is referred to by the common names wire weed or sea nymph, and is a seagrass found in coastal waters of southern and western Australia.

<i>Halophila ovalis</i> Species of aquatic plant

Halophila ovalis, commonly known as paddle weed, spoon grass or dugong grass, is a seagrass in the family Hydrocharitaceae. It is a small herbaceous plant that naturally occurs in sea beds and other saltwater environments in the Indo-Pacific. It was introduced as isolated populations in Florida, Cuba and Antigua.

Posidonia ostenfeldii is a species of seagrass that occurs in the southern waters of Australia.

<i>Posidonia</i> Genus of aquatic plants

Posidonia is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia.

<i>Posidonia oceanica</i> Species of marine plant

Posidonia oceanica, commonly known as Neptune grass or Mediterranean tapeweed, is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free floating and known in Italy as "the olive of the sea". Balls of fibrous material from its foliage, known as egagropili or Neptune balls, wash up to nearby shorelines.

Posidonia coriacea is a species of seagrass that occurs in the southern waters of Australia.

The Seagrasses of Western Australia are submerged flowering plants found along the coast, around islands, and in Estuaries of Western Australia. The region contains some of the largest seagrass meadows in the world, and is the most diverse in the number of species. The variety of habitats along its western and southern coasts is often soft sands in shallow subtropical waters, ideal for these plants.

Posidonia robertsoniae is one of the seagrasses of Western Australia, submerged flowering plants that occur in the southern coastal waters.

Ribbon weed may refer to:

<i>Zostera marina</i> Species of aquatic plant

Zostera marina is a flowering vascular plant species as one of many kinds of seagrass, with this species known primarily by the English name of eelgrass with seawrack much less used, and refers to the plant after breaking loose from the submerged wetland soil, and drifting free with ocean current and waves to a coast seashore. It is a saline soft-sediment submerged plant native to marine environments on the coastlines of northern latitudes from subtropical to subpolar regions of North America and Eurasia.

<i>Cymodocea nodosa</i> Species of plant in the family Cymodoceaceae

Cymodocea nodosa is a species of seagrass in the family Cymodoceaceae and is sometimes known as little Neptune grass. As a seagrass, it is restricted to growing underwater and is found in shallow parts of the Mediterranean Sea and certain adjoining areas of the Atlantic Ocean.

<span class="mw-page-title-main">Posidonia clingfish</span> Species of fish

The Posidonia clingfish is a species of clingfish native to the Australia coast. This species grows to a length of 2 centimetres (0.79 in) SL. Pale green to pale blue with fine spots forming dark reticulations on back and sides, larger blue spots often on back, and a pinkish to brown line from snout to gill cover. The posidonia clingfish is endemic to southern Australia where its range extends from Corner Inlet in Victoria west as far as Rottnest Island in Western Australia. It occurs down to a depth of 10 metres (33 ft) where it is found on macroalgae and within seagrass beds, its favoured substrate to adhere to is the leaves of the sea grass Posidonia australis. This species is the only known member of its genus and was described by John C. Briggs in 1993 with a type locality of Fiddler's Bay which is 16 kilometres south of Tamby Bay in South Australia. Briggs gave the species the specific name hutchinsi in honour of the ichthyologist Barry Hutchins of the Western Australia Museum in Perth, Western Australia.

Halophila baillonis is a species of aquatic plant in the family Hydrocharitaceae. It is referred to by the common name clover grass. It is native to Brazil, Cayman Islands, Colombia, Costa Rica, Jamaica, Leeward Islands, Netherlands Antilles, Panama, Puerto Rico, Trinidad and Tobago, and Venezuela. It is listed on the IUCN Red List as "vulnerable" due to its naturally rare occurrence and fragmented populations.

<span class="mw-page-title-main">Vivipary</span> Plant seeds developing before detachment

In plants, vivipary occurs when seeds or embryos begin to develop before they detach from the parent. Plants such as some Iridaceae and Agavoideae grow cormlets in the axils of their inflorescences. These fall and in favourable circumstances they have effectively a whole season's start over fallen seeds. Similarly, some Crassulaceae, such as Bryophyllum, develop and drop plantlets from notches in their leaves, ready to grow. Such production of embryos from somatic tissues is asexual vegetative reproduction that amounts to cloning.

<span class="mw-page-title-main">Posidonia australis seagrass meadows of the Manning-Hawkesbury ecoregion</span> Australian endangered ecological community

Posidonia australis seagrass meadows of the Manning-Hawkesbury ecoregion is an endangered ecological community, listed under the EPBC Act of the Commonwealth of Australia on 7 May 2015

References

  1. 1 2 Short, F.T.; Carruthers, T.J.R.; Waycott, M.; Kendrick, G.A.; Fourqurean, J.W.; Callabine, A.; Kenworthy, W.J.; Dennison, W.C. (2010). "Posidonia australis". IUCN Red List of Threatened Species . 2010: e.T173333A6993340. doi: 10.2305/IUCN.UK.2010-3.RLTS.T173333A6993340.en . Retrieved 19 November 2021.
  2. "It's a clone, and it's massive: World's largest plant found off WA coast". Australia: ABC News. 31 May 2022. Retrieved 11 October 2023.
  3. "Posidonia australis". FloraBase . Western Australian Government Department of Biodiversity, Conservation and Attractions.
  4. 1 2 Mike van Keulen. "The genus Posidonia König (nom. cons.) (Posidoniaceae)". Murdoch University.
  5. Elizabeth Sinclair. What happens when (plant) sex fails? Atlas of Science, 2016
  6. "Humble plants may save the planet". University of Technology, Sydney. 14 August 2013. Archived from the original on 19 August 2013. Retrieved 15 August 2013.
  7. Katie Hunt. "World's largest plant discovered in Australia". CNN. Retrieved 2 June 2022.
  8. 1 2 Edgeloe, Jane M.; Severn-Ellis, Anita A.; Bayer, Philipp E.; Mehravi, Shaghayegh; Breed, Martin F.; Krauss, Siegfried L.; Batley, Jacqueline; Kendrick, Gary A.; Sinclair, Elizabeth A. (1 June 2022). "Extensive polyploid clonality was a successful strategy for seagrass to expand into a newly submerged environment". Proceedings of the Royal Society B: Biological Sciences. 289 (1976): 20220538. doi:10.1098/rspb.2022.0538. PMC   9156900 . PMID   35642363 . Retrieved 1 June 2022.
  9. 1 2 3 4 Readfearn, Graham (1 June 2022). "Scientists discover 'biggest plant on Earth' off Western Australian coast". The Guardian . Retrieved 1 June 2022.
  10. Kilvert, Nick (1 June 2022). "World's largest plant discovered right under our noses in Western Australia". Australia: ABC News. Retrieved 1 June 2022.
  11. Hooker, J. D. (1860). The botany of the Antarctic voyage of H.M. discovery ships Erebus and Terror. Vol. III Flora Tasmaniæ II Monocotyledones and Acotyledones. p. 43.
  12. Australian Government. "Species Profile and Threats Database: Posidonia australis seagrass meadows of the Manning-Hawkesbury ecoregion". Department of Agriculture, Water and the Environment.