''Halodule uninervis'' is a species of

seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...

in the family

Cymodoceaceae Cymodoceaceae is a family of flowering plants, sometimes known as the "manatee-grass family", which includes only marine species. The 2016 APG IV does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. The ...

. It is native to the western

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

s. Common names include narrowleaf seagrass in

English English usually refers to: * English language * English people English may also refer to: Culture, language and peoples * ''English'', an adjective for something of, from, or related to England * ''English'', an Amish ter ...

and ''a'shab bahriya'' in

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

.Guiry, M. D. & G. M. Guiry. 2013
''Halodule uninervis'' (Forsskål) Ascherson.
AlgaeBase. National University of Ireland, Galway. Accessed 28 June 2013.

Distribution and habitat

This is a common plant of the

sublittoral zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

in its range, growing in depths up to 20 meters in

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

s, on

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

s, and in many other types of marine habitat just offshore. It is known from Asian waters along the coasts of

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, and other nations. It occurs on

Pacific Islands The Pacific islands are a group of islands in the Pacific Ocean. They are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of several ...

such as

Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...

. It occurs along the

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

n Pacific coast, including the

Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system, composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...

. It can be found along Indian Ocean coastal regions from Australia to

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

to eastern Africa. It is resident in the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

and

Persian Gulf The Persian Gulf, sometimes called the Arabian Gulf, is a Mediterranean seas, mediterranean sea in West Asia. The body of water is an extension of the Arabian Sea and the larger Indian Ocean located between Iran and the Arabian Peninsula.Un ...

Description

This species is a flowering plant spreading via a branching

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

that roots at the nodes. It produces erect stems and alternately arranged leaves. The narrow, toothed leaf blades are up to 15 centimeters long and usually roughly a millimeter wide,''Halodule uninervis''.
Flora of China. though leaf width is variable and can be up to 7 millimeters. Each leaf has a sturdy sheath up to 3.5 centimeters long. The tip of the leaf blade has three teeth.''Halodule uninervis''.
New South Wales Flora Online. National Herbarium, Royal Botanic Garden, Sydney. Plants of this family are

dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

. The male flower is borne on a short peduncle and is enclosed in a leaf. The tiny

anther The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s are red. The fruit is about 2 millimeters long. Leaf

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

changes according to habitat type. The leaves are wider in deeper waters. There are apparently two morphs, a narrow leaf and a wide leaf, rather than a continuous range. The narrow leaf type is found closer to shore where it is exposed more often. The wide leaf type is found in deeper areas with cloudier waters. Plants that receive less light may need more leaf blade area to perform enough

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

.Hedge, S., et al. (2009)
Temporal and spatial morphological variability of the seagrasses ''Halophila ovalis'' and ''Halodule uninervis'' throughout the Great Barrier Reef region: Preliminary analysis.
Report to the Marine and Tropical Sciences Research Facility, Department of the Environment, Water, Heritage and the Arts. Reef and Rainforest Research Centre Limited, Cairns.

Biology

This grass forms dense carpets or meadows on the substrate, sometimes mixing with other seagrasses and

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

s. It occupies the lower

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

, and it is less tolerant of exposure to air than are plants of the upper intertidal zone such as ''

Thalassia hemprichii ''Thalassia hemprichii'', called Pacific turtlegrass, is a widespread species of seagrass in the genus '' Thalassia'', native to the shores of the Indian Ocean, the Red Sea, and the western Pacific Ocean. Its growth rate increases with CO2 enrich ...

''. It desiccates quickly. It is also sensitive to

ultraviolet radiation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...

. These factors restrict it to deeper intertidal waters than some other plants.Lan, C. Y., et al. (2005)
Measurement of chlorophyll fluorescence reveals mechanisms for habitat niche separation of the intertidal seagrasses ''Thalassia hemprichii'' and ''Halodule uninervis''.
''Marine Biology'' 148(1) 25-34. It is a

euryhaline Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the short-finned molly, '' Poecilia sphenops'', which can live in fresh water, brackish water, or salt water. The green crab ('' Carcinus m ...

species, tolerating a wide

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

range.Bensam, P. and T. R. Udhayashankar
Colonisation and growth of the sea grasses, ''Halodule uninervis'' (Forskal) Ascherson and ''Halophila ovalis'' (R. Brown) Hooker f. in marine culture ponds at Mandapam.
The Second Indian Fisheries Forum Proceedings. Mangalore, India. May 27–31, 1990. 51-53.

Ecology

This species is an important food for the

dugong The dugong (; ''Dugong dugon'') is a marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest ...

.Lipkin, Y. (1975)
Food of the Red Sea dugong (Mammalia: Sirenia) from Sinai.
''Israel Journal of Zoology'' 24(3-4) 81-98. The grass grows in the Masirah Channel, a waterway between

Masirah Island Masirah Island (), also referred to as Mazeira Island, is an island off the east coast of mainland Oman in the Arabian Sea, and the largest island of the country. Administratively, it forms one of the five Provinces of Oman, provinces (''Wilaya ...

and mainland

Oman Oman, officially the Sultanate of Oman, is a country located on the southeastern coast of the Arabian Peninsula in West Asia and the Middle East. It shares land borders with Saudi Arabia, the United Arab Emirates, and Yemen. Oman’s coastline ...

, where it is an important food for the

green sea turtle The green sea turtle (''Chelonia mydas''), also known as the green turtle, black (sea) turtle or Pacific green turtle, is a species of large sea turtle of the family Cheloniidae. It is the only species in the genus ''Chelonia''. Its range exte ...

.Jupp, B. P., et al. (1996)
Distribution, abundance, and species composition of seagrasses at several sites in Oman.
''Aquatic Botany'' 53(3) 199-213. This is a

pioneer species Pioneer species are resilient species that are the first to colonize barren environments, or to repopulate disrupted biodiverse steady-state ecosystems as part of ecological succession. Various kinds of events can create good conditions for pi ...

. It has been observed on high-sediment, rapidly evolving substrates in Australia and Indonesia. This species is known to be hybridized to ''Halodule'' ''pinifolia'' in Okinawa, Japan.Ito, Y., and Nr. Tanaka (2011
Hybridisation in a tropical seagrass genus, Halodule (Cymodoceaceae), inferred from plastid and nuclear DNA phylogenies
. Telopea 13: 219-231.

Conservation

This plant is widely distributed and it is common throughout its range. In general its populations are stable, though it may be decreasing in localized areas, such as the coast of

Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...

, and it fluctuates in some Australian waters. It is affected by some degradation of habitat by forces such as coastal development,

siltation Siltation is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary o ...

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to th ...

, weather events and tidal action, predation, parasites, disease,

trawling Trawling is an industrial method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch di ...

and other fishing practices,

dredging Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing d ...

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

, and

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

. Conservation plans are in effect in various regions. Populations are monitored in the

United Arab Emirates The United Arab Emirates (UAE), or simply the Emirates, is a country in West Asia, in the Middle East, at the eastern end of the Arabian Peninsula. It is a Federal monarchy, federal elective monarchy made up of Emirates of the United Arab E ...

. It grows within the bounds of several marine parks and reserves in Africa. Populations can be disturbed only with permits in parts of Australia. Large beds are protected in

Hat Chao Mai National Park Hat Chao Mai National Park is a protected area located in the Sikao and Kantang Districts of Trang Province, Thailand. It is a marine national park. Established in 1981, it is an IUCN Category II protected area with coral reefs, and an area mea ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

References

External links

*WoRMS. (2013)
''Halodule uninervis'' (Forsskål) Ascherson, 1882.
In: Guiry, M. D. & G. M. Guiry. AlgaeBase. National University of Ireland, Galway. World Register of Marine Species. Accessed 28 June 2013. {{Taxonbar, from=Q10880391 Cymodoceaceae Biota of the Indian Ocean Flora of the Pacific Taxa named by Pierre Edmond Boissier Taxa named by Peter Forsskål