Mangroves

Scientific name

• Ceriops australis extends north from south-east Queensland
• Ceriops tagal and Ceriops decandra are found in north Queensland.

Description

• The base of the tree is buttressed (a distinguishing feature).
• The bark is yellowish or light brown to grey, and roughened by corky lenticels (air pores) along the trunk.
• Leaves grow to 7cm long and 4cm wide, are oval-shaped with a notched tip and are slightly curled under at the edges. They are arranged opposite one another in groups at the ends of branchlets.
• Flowers are white and about 6mm long, and appear in pairs at the base of the leaves.

Distribution

• Ceriops species are found throughout the Indo-West Pacific.
• Ceriops australis extends north of the Tweed River on the east coast of Queensland across northern Australia to Exmouth in Western Australia.

Salt tolerance

• This species excludes salts through its roots as water is taken up.

Habitat

• Commonly found on firm, peaty, well drained clays, clayey mud or sand clays at the upper tidal limit of the mangrove shore.
• Yellow mangrove also grows in soils that are poorly drained and frequently inundated by the tides, where it forms low, open shrub lands.

Life cycle

• Ceriops australis can grow from a shrub of 0.5–1m to a small slender tree of 2–7m and up to 10m in north Queensland.
• Ceriops tagal and Ceriops decandra can grow to 25m and 15m respectively.
• Flowers between September and December.
• Flowers open in the late afternoon and are pollinated by night-flying insects, such as moths.
• Between December and January brown, pear-shaped fruit that is 10–12mm long appear.
• A smooth, tapered, cylindrical propagule of 10–15cm protrudes through the fruit wall and is suspended vertically beneath the fruit.
• This propagule often takes on a reddish colour as it matures until it is shed into the water with the fruit.

Scientific name

• Excoecaria agallocha

Description

• These mangroves grow up to 15m, as shrubs or trees.
• Bark is grey to fawn brown, marked with longitudinal rows of corky brown air pores (lenticels).
• It has surface roots, which allow the uptake of oxygen  when exposed to air at low tide.
• The major feature of this mangrove is the milky sap which exudes from the plant when branches or leaves are broken. The sap is poisonous and can cause severe skin irritation and temporary blindness if contact is made with the eyes.
• Any salt taken up accumulates in the leaves and may be removed as leaves grow old and fall from the plant.
• Leaves are pale green to yellowish and measure from 5 to 11 cm in length and 2 to 4 cm in width.
• The shape of the leaves are basically oval, with a pointed tip, rounded at the base and often finely toothed at the edges and are attached alternately on the stems.

Distribution

• Milky mangroves can be found from northern New South Wales, through Queensland and Northern Territory to Western Australia.

Habitat

• In Queensland, it is a mangrove of the upper tidal limits and grows at the landward fringe of the mangrove community.
• It is often found on small sandy ridges in mixed stands of mangroves.
• It is often associated with the grey mangrove, the white-flowered black mangrove (Lumnitzera racemosa), and the river mangrove (Aegiceras corniculatum).

Life cycle

• Minute flowers 2mm in diameter appear from October to April.
• Male flowers and female flowers are located on separate trees. Male flowers are on inflorescences (groups or clusters of flowers arranged on a stem composed of a main branch or arrangement of branches) 7–11 cm long and female flowers are on inflorescences up to 3cm long.
• Fruiting occurs throughout the year with the appearance of small three-lobed fleshy green capsules about 5mm in diameter arranged in clusters.
• Each lobe contains a single seed which is released from the capsule as it opens.
• Seeds are buoyant due to an air space within the seed coat. They float with the tides and currents until a suitable soil is encountered where they can germinate and seedlings can develop.

Scientific name

• Avicennia marina

Description

• Grey mangrove generally grows to 25m high, though trees of 10–15m are common in Queensland under favourable conditions.
• It has a large trunk, covered by light grey, finely fissured bark that supports a spreading leafy crown, and the peg-like roots of the grey mangrove can form a dense covering over the ground.
• Leaves measure up to 8cm in length and 5cm in width, and are oval, pointed and arranged opposite one another on the stems.
• Leaves are a glossy green above with a distinctive pale and slightly hairy, grey underside.
• Stomata (pores) and salt glands are scattered over the entire leaf surface but are more abundant on the underside.
• Flowers are small and orange, and appear in clusters.
• A distinguishing feature of this species is the numerous spongy pencil-like pneumatophores (peg-like roots) that spread out from the base of the trunk. Pneumatophores originate from horizontal, underground lateral roots and grow vertically through the soil surface to enable the mangrove roots to breathe.
• As a pioneer species, grey mangrove is very tolerant of extreme saline conditions and actively resists the uptake of salt at the roots. It can withstand short periods of inundation by freshwater or hypersaline water (salinity exceeding that of seawater).
• All mangroves are susceptible to extended periods of waterlogging, with death occurring within 14 days.
• Grey mangrove can stabilise river banks and channels to provide areas for spat settlement in oyster aquaculture.
• Queensland's grey mangrove timber was once recognised as an important resource for commercial oyster growers in the 1900s and this led to the protection of mangroves under early fisheries legislation.

Distribution

• It is the most common and widespread mangrove found along the mainland coast of Australia. It is the only mangrove species able to withstand the cooler climates of South Australia and Victoria.

Habitat

• Grey mangrove occurs in intertidal zones on a range of soft muds to sandy soils and commonly colonises developing mud banks.
• It’s common along the tidal margins of estuaries and saline or brackish river areas where it may grow with river, red and other mangrove species.

Life cycle

• The periods of flowering and fruiting times vary with different latitudes. In Queensland, flowering periods may occur from mid-summer through autumn, with fruiting periods from autumn through to spring.
• The pale green, flattened fruits are 3 cm long and 2 cm wide and consist of a thin, hairy seed coat and enclose two closely folded seed leaves.
• Seeds germinate while attached to the tree (vivipary), which allows for quick establishment once the seed settles.

Scientific name

• Rhizophora stylosa

Description

• Trees are usually 4–5m high, but can grow up to 20m in North Queensland
• The main trunk is erect and covered by rough, reddish-brown bark.
• Stout, large arching prop roots are characteristic, and these support the main trunk.
• Prop roots contain numerous lenticels (air pores) on their surfaces. The lenticels are air-filled spaces that connect with underground root structures and help with gas exchange.
• Aerial roots are produced from the tree's lower branches and help mangrove breathe. These do not take root, even after reaching the soil.
• Leaves are oval-shaped, thick and leathery, and are up to 15cm in length and 6cm in wide.
• Leaves are dark green with numerous small, reddish-brown dots on the lower surface and a small deciduous pointed tip.
• Small, creamy-white flowers grow in branching pairs while the leaves are arranged in opposite pairs on the stem.
• This species eliminates salt at its roots as water is taken up. Excess salt that finds its way into the plant is stored in the leaves, and removed from the plant when the leaves die and fall from the tree.

Distribution

• Red mangroves grow along coasts in northern Australia, from the Richmond River in New South Wales to Shark Bay in Western Australia.

Habitat

• It prefers soft, well drained muddy soils but can establish on rock or coral-based sandy soils and is a dominant species of lower tidal mangrove forests.
• It is commonly seen along the lower tidal reaches of rivers and immediately behind the seaward fringe of mangroves, sometimes with grey and yellow mangroves.
• Red mangroves form extensive, often pure stands around the shores of shallow protected bays, estuaries and inlets.

Life cycle

• Flowering peaks from late summer through to mid autumn, and a single-seeded, brown, oval-shaped fleshy fruit will be produced during summer.
• Seeds germinate on the tree (vivipary), which results in the appearance of a long, green, rounded propagule (seedling) about 30cm long.
• Red mangrove propagules grow up to 30cm in length before dropping from the tree.
• The propagule protrudes through the wall of the fruit to hang vertically beneath it. This buoyant germinated seed is the first stage of the root system.

Scientific name

• Bruguiera gymnorhiza 

Description

• Orange mangroves reach up to 25m in height, with rough, dark grey to black coloured bark.
• Buttressing is sometimes present at the base of the trunk.
• Its key feature is its knobbly, bent knee-shaped roots (pneumatophores) help allow gaseous exchange.
• These roots develop from the underground root system and protrude through the soil surface at intervals.
• Some salt is taken up from the roots, but is removed as it accumulates in the leaves that grow old and fall from the plant.
• The propagule protrudes through the wall of the fruit to hang vertically beneath it. This buoyant germinated seed is the first stage of the root system.
• Large, smooth, thick leaves that can grow to 24cm long and 9cm wide. They are elliptical in shape and arranged in opposite pairs on the ends of branches.
• The upper leaf surface is glossy and dark green, while the underside is paler green. The leaf stalk is tinged and red flowers appear at the base of the leaves.

Distribution

• It is widespread across northern Australia. It ranges along the east coast from the Clarence River in New South Wales to Cape York and west to Darwin in the Northern Territory.

Habitat

• This species prefers firm, well drained, muddy soils that experience only a few high tides each month. It is often the most landward of mangroves and is common in areas subject to freshwater influence, such as brackish reaches of tidal streams.

Life cycle

• After flowering, single-seeded fleshy fruits appear from August to February.
• Seeds suspend vertically beneath a red, cup-shaped flower.
• After germinating and falling from the tree, the seed floats to be dispersed by the movement of the tides.

Scientific name

• Aegiceras corniculatum

Description

• River mangrove usually grows as a bushy shrub 2–3m high, but may grow to a small tree with several slender trunks up to 5m high.
• The bark is smooth and dark grey.
• Leaves are spoon-shaped with a rounded tip, and are glossy green above and paler green below. They occur alternately along the stem, while the surface is covered with minute salt glands that excrete salt from the plant.
• Clusters of white flowers may appear with a smell similar to rotten bananas.
• Roots along the soil surface are exposed to air at low tide and help the uptake of oxygen. Prominent lenticels (air pores) at the base of each trunk also help with atmospheric gas exchange.
• Salt is extruded by glands on the leaves, which accumulates over time resulting in a fine film of white salt crystals on leaf surfaces. These crystals are most often seen during prolonged dry weather and are the primary characteristic by which river mangrove can be identified.

Distribution

• The species is distributed throughout South East Asia, and extends from southern New South Wales along the east coast of Australia and along the west coast from Cape York to Shark Bay.
• It is common along banks in southern Queensland in the upper tidal reaches of creeks and rivers where it is frequently found beneath stands of grey mangrove.

Habitat

• Healthy river mangroves can tolerate fresh and salty water and grows on poorly drained mud that is periodically inundated by saline or brackish water and as a shrubby hedge along river bank.
• It may also form pure, dense stands in the centre and landward zones of mangrove forests.

Life cycle

• Most flowering occurs in winter and early spring.
• The single-seeded fruit is small, curved, elongated and fleshy, and appears between summer and autumn. Seeds germinate on the tree (vivipary).