Australian Mangroves and Wetlands Ecosystem

This page is an extract of a script that is part of the video series
"The Living Landscape-an Australian Ecosystems Series".
Visit all ecosystems.

MANGROVES & WETLANDS

SNAIL SEARCHING FOR PREY
Mangroves are a breeding ground and nursery for many kinds of animals. At the bottom, in the mud, are molluscs and worms, burrowing in the soil and moving about to feed when the tide is out.

MALE CRAB ADVERTISE WITH AN OVERSIZE NIPPER
When the tide is out, crabs cope with the period without water by excavating burrows in the mud. They use the water in the burrows to keep their gills moist, or to replenish water in their gill chambers. The burrows are also used as hiding places from predators, and to keep the crabs out of the hot sun.

Mud crab over 3kg MUD CRAB
A mud crab can grow to over 3kg and are very good to eat.

A TREE SNAIL ON MANGROVES
When the tide comes in, so do the fish. They come in all sizes, from microscopic to large specimens. They feed on algae, leaves, tree snails - and in some cases, on each other.

Out of the water, spiders and molluscs live in the trees. The seven-horned mangrove spider, for example, lives exclusively in the mangroves.

FLYING FOX OR FRUIT BAT
Fruit bats are one of the few mammals in the mangrove forests. By day they camp in the mangroves, and move out to feed at night, searching for blossoms, fruit and nectar.

Ibis & Herons IBIS AND HERONS FEEDING
There are also many birds in the mangroves: waterbirds like ibis, herons and other waders. These birds roost in the mangroves, and the estuaries provide a bountiful feeding ground that yields a wide variety of food such as worms, molluscs, crustaceans and an abundance of fish.

Brolga BROLGA. Found only in Australia & New Guinea
In the freshwater marshes back towards the mountains there may be brolgas, tall cranes that perform spectacular and graceful dances. The brolga chicks hatch in floating nests of reeds and sticks, and are soon able to explore their environment. The brolgas stilt-like legs and long beaks are perfect for wading in the marshes and spearing the frogs, reptiles and rodents they live on.

Mangroves live in a harsh environment at the very edge of the sea, where land meets water. In these areas, the main problems plants have to face are the salinity, the lack of oxygen in the shallow and water-logged (or anaerobic) soils, and the difficulty of colonising areas that are regularly covered by moving water.

SALT CRYSTALS ON A MANGROVE LEAF
The mangroves have developed ways of coping with excess salt: either excluding it, secreting it, or accumulating and then disposing of it.

The grey mangrove is a salt excreter. Tissues in the roots and lower stem also have a secondary use, filtering out some salts. Pneumatophores, aerial breathing roots that look rather like pegs, absorb oxygen at low tide.

ARCHING PROP ROOTS
The red mangrove copes with the conditions in rather different ways. Its roots are quite different from the grey mangrove's: arching, branching prop roots that spread out widely, absorbing oxygen and helping the tree to breathe. The red mangrove is a salt excluder. Tissues in its roots and lower stem filter out salts and allow the tree to take up fresh water.

A HYPOCOTYL
The red and yellow mangroves method of reproduction involves the development of a seedling stem, a hypocotyl, that grows as long as 30cm and hangs beneath the fruit. When it falls, it anchors itself in the mud and grows.