Posidonia australis
Encyclopedia
Posidonia australis is a species of seagrass
that occurs in the southern waters of Australia. It is sometimes referred to as Fibreball Weed. The marine plant forms large meadows that are considered to be of high importance to the environmental conservation of the region. Balls of decomposing detritus from the foliage of the plant are found along nearby shore-lines.
s and roots provide stability in the sands it occupies, erect rhizomes and leaves reduce the accumulation of silt.
The leaves are ribbon-like and between 11 an 20 mm wide. They are bright green, perhaps becoming browned with age. The terminus of the leaf is rounded or absent through damage. They 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 are found on each spike. The plant pollinates by hydrophily
, by dispersing in the water.
is 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. A sign of a nearby occurrence of Posidonia
is the presence of masses of decomposing leaves on beaches, these form fibrous balls.
, is found in the mediterranean sea.
The binomial 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.
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
that occurs in the southern waters of Australia. It is sometimes referred to as Fibreball Weed. The marine plant forms large meadows that are considered to be of high importance to the environmental conservation of the region. Balls of decomposing detritus from the foliage of the plant are found along nearby shore-lines.
Description
A flowering plant occurring in dense meadows, or along channels, in white sand. It is found at depths from 1 metre to 15 metres. Subsurface rhizomeRhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
s and roots provide stability in the sands it occupies, erect rhizomes and leaves reduce the accumulation of silt.
The leaves are ribbon-like and between 11 an 20 mm wide. They are bright green, perhaps becoming browned with age. The terminus of the leaf is rounded or absent through damage. They 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 are found on each spike. The plant pollinates by hydrophily
Hydrophily
Hydrophily is a fairly uncommon form of pollination whereby pollen is distributed by the flow of waters, particularly in rivers and streams. Hydrophilous species fall into two categories: those that distribute their pollen to the surface of water, and those that distribute it beneath the...
, by dispersing in the water.
Distribution
This species is found in waters around the southern coast of Australia. In Western AustraliaWestern Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
is occurs in the Shark Bay
Shark Bay, Western Australia
Shark Bay is a World Heritage Site in the Gascoyne region of Western Australia. It is an area centred approximately on , 800 kilometres north of Perth, on the westernmost point of Australia. An expedition led by Dirk Hartog happened upon the area in 1616, becoming the second group of Europeans...
region, around islands of the Houtman Abrolhos
Houtman Abrolhos
The Houtman Abrolhos is a chain of 122 islands, and associated coral reefs, in the Indian Ocean off the west coast of Australia. Nominally located at , it lies about eighty kilometres west of Geraldton, Western Australia...
, and southward along the coast of the Swan Coastal Plain
Swan Coastal Plain
The Swan Coastal Plain in Western Australia is the geographic feature which contains the Swan River as it travels west to the Indian Ocean. The coastal plain continues well beyond the boundaries of the Swan River and its tributaries, as a geological and biological zone, one of Western Australia's...
. The species is recorded at the edge of the Esperance Plains
Esperance Plains
Esperance Plains, also known as Eyre Botanical District, is a biogeographic region in southern Western Australia. Located on the south coast between the Avon Wheatbelt and Hampton regions, and bordered to the north by the Mallee region, it is a plain punctuated by granite and quartz outcrops and...
, the Archipelago of the Recherche
Archipelago of the Recherche
Archipelago of the Recherche is a group of 105 islands, and over 1200 "obstacles to shipping", off the southern coast of Western Australia. The islands, also known as the Recherche Archipelago, stretch from East to West and to off-shore....
, 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. A sign of a nearby occurrence of Posidonia
Posidonia
Posidonia is a genus of flowering plants. It contains two to nine species of marine plants , found in the seas of the Mediterranean and around the south coast of Australia....
is the presence of masses of decomposing leaves on beaches, these form fibrous balls.
Taxonomy
This species is contained by the Posidoniaceae family, one of eight occurring in Australia. The ninth member, Posidonia oceanicaPosidonia oceanica
Posidonia oceanica 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'...
, is found in the mediterranean sea.
The binomial for this species, Posidonia , is given for the god of the seas Poseidon
Poseidon
Poseidon was the god of the sea, and, as "Earth-Shaker," of the earthquakes in Greek mythology. The name of the sea-god Nethuns in Etruscan was adopted in Latin for Neptune in Roman mythology: both were sea gods analogous to Poseidon...
, and australis refers to the southern distribution.
The species was first described by Joseph Hooker
Joseph Dalton Hooker
Sir Joseph Dalton Hooker OM, GCSI, CB, MD, FRS was one of the greatest British botanists and explorers of the 19th century. Hooker was a founder of geographical botany, and Charles Darwin's closest friend...
in Flora Tasmaniae.
External links
- Posidoniaceae in L. Watson and M. J. Dallwitz (1992 onwards) The families of flowering plants.
- National Center for Biotechnology Information
- Germplasm Resources Information Network: Posidonia