Avicennia marina, commonly known as grey mangroveorwhite mangrove, is a species of mangrove tree classified in the plant family Acanthaceae (formerly in the VerbenaceaeorAvicenniaceae). As with other mangroves, it occurs in the intertidal zones of estuarine areas.
In Australia, it extends much farther south than other mangroves, occurring in every mainland state.
Its distribution is disjunct in Western Australia; the population of the Abrolhos Islands is 300 km (190 mi) further south than the nearest population of Shark Bay. Another mangrove system is found even further south (500 km) at Bunbury. This colonisation of southerly climes may have occurred relatively recently, perhaps several thousand years ago, when they were transferred by the Leeuwin Current.[15] The most inland occurrence of mangroves in Australia is a stand of grey mangroves in the Mandora Marsh, some 60 km from the coast.
Excreted salt on the underside of a Avicennia marina var. resinifera leafFlower
Grey mangroves grow as a shrub or tree to a height of 3 to 10 m (9.8 to 32.8 ft), or up to 14 m in tropical regions. The habit is a gnarled arrangement of multiple branches. It has smooth light-grey bark made up of thin, stiff, brittle flakes. This may be whitish, a characteristic described in the common name. The leaves are thick, 5 to 8 cm (2.0 to 3.1 in) long, a bright, glossy green on the upper surface, and silvery-white, or grey, with very small matted hairs on the surface below. As with other Avicennia species, it has aerial roots (pneumatophores); these grow to a height of about 20 cm (5 in), and a diameter of 1 cm. These allow the plant to absorb oxygen, which is deficient in its habitat. These roots also anchor the plant during the frequent inundation of seawater in the soft substrate of tidal systems. The flowers range from white to a golden yellow colour, are less than 1 cm across, and occur in clusters of three to five. The fruit contains large cotyledons that surround the new stem of a seedling. This produces a large, fleshy seed, often germinating on the tree and falling as a seedling.[16] The grey mangrove can experience stunted growth in water conditions that are too saline, but thrive to their full height in waters where both salt and fresh water are present. The species can tolerate high salinity by excreting salts through its leaves.[15]
Avicennia marina var. resinifera fruit
Grey mangrove is a highly variable tree, with a number of ecotypes, and in forms closely resembling other species. It has been reported to tolerate extreme weather conditions, high winds, and various pests and diseases. It is a pioneer in muddy soil conditions with a pH value of 6.5 to 8.0, but is intolerant of shade. A number of botanists have proposed division of the species, but currently three subspecies are recognised:
A. m. subsp. australasica
A. m. subsp. eucalyptifolia
A. m. subsp. marina
References
^ abDuke, N., Kathiresan, K., Salmo III, S.G., Fernando, E.S., Peras, J.R., Sukardjo, S., Miyagi, T., Ellison, J., Koedam, N.E., Wang, Y., Primavera, J., Jin Eong, O., Wan-Hong Yong, J. & Ngoc Nam, V. (2010). Avicennia marina. The IUCN Red List of Threatened Species 2010: e.T178828A7619457. http://doi.org/10.2305/IUCN.UK.2010-2.RLTS.T178828A7619457.en. Downloaded on 07 September 2018.
^"Harra Protected Area". UNESCO » Culture » World Heritage Centre » The List » Global Strategy » Tentative Lists. Retrieved 6 February 2016.
^Naidoo, Gonasageran (2016). "The mangroves of South Africa: An ecophysiological review". South African Journal of Botany, Volume 107, November 2016, Pages 101-113
Data related to Avicennia marina at Wikispecies
Media related to Avicennia marina at Wikimedia Commons
