Australia is one of the driest continents in the world. The amount of water in rivers, lakes and wetlands can vary greatly from year to year, depending on rainfall and climate. Water is an essential resource to all ecosystems and living things, including humans, animals and plants.
Rivers, lakes and wetlands are all unique and important homes or habitats for many species including plants, fish, birds, reptiles and mammals. These habitats provide food and shelter for many of these species.
In Australia, and all around the world, watery habitats are coming under increasing threat due to population growth, pollution and development.
Below are some species that rely on our waterways to stay healthy and alive.
Mary River Cod (Maccullochella peelii mariensis)
The Mary River Cod can grow up to 36 kg!
Only found in the Mary River System in south-east Queensland, the Mary River Cod is one of Australia's most endangered fish. The Cod likes to live in deep, shaded, slow flowing pools that have snags, log jams, boulders and rock ledges that can be used for protection. It is thought that they use submerged hollow logs as breeding sites.
The Mary River Cod can grow up to 36kg, but they usually don't grow over 4.5 kg. They feed on other fish, yabbies and other small crustaceans, but they have been known to eat birds, bats and water rats!
Their habitat has been reduced and broken up. Erosion in the Mary River catchment through activities such as land clearing has silted parts of the river and filled in the deep pools. The removal of native vegetation from the stream banks also means that there is less shade and fewer logs falling into the water to create Mary River Cod habitat.
Blue Mountain's water skink (Eulamprus leuraensis)
This endangered, semi aquatic reptile is known from less than 30 places in the Blue Mountains in New South Wales. They live in swamps with permanently wet, boggy soils and eat grasshoppers, flies, moths, weevils and wasps. Females give birth to live young in late December.
The Blue Mountain's water skink are found in clumps of swamp sedges and herbs, particularly when there is a large number of the Flax-leaf Heath Myrtle Baeckea linifolia and Tetrarrhena turfosa, a plant which doesn't have a common name.
Water plays a crucial role in the survival of the Blue Mountain's water Skink. Water polluted through rubbish disposal, stormwater runoff and septic tank discharge means that there are fewer insects that the Skink relies on for food. Because the populations are small and broken up, further disturbance could wipe out entire local populations of the Skink. As well as pollution, lowering of the water table, sedimentation, predation by cats and disturbance by people all have an impact on the Blue Mountain's Water Skink habitat.
The aquatic root mat communities of the Leeuwin-Naturaliste Ridge Caves
The rare and complex aquatic root mat communities of the limestone caves underneath the Leeuwin-Naturaliste Ridge in Western Australia are home to a rich assortment of wildlife. These communities are made up of freshwater crayfish, insects, crustaceans, water bears (tardigrades), rotifers (tiny aquatic organisms), mites, microscopic worms and fungi. They all live in the mat of eucalyptus and peppermint tree roots that come down through the soil in search of water from the permanent underground streams.
More than 37 species have been found in four caves. At least half of these are newly discovered and many are yet to be identified.
Normally, caves don't support permanent life because they can't sustain a reliable food source. In these communities, the tree roots, which are able to reach the water found in the shallow caves, create a habitat for microscopic fungi. These fungi provide a food source for other organisms in the community which in turn provide a food source for predators. Parasites, scavengers, and debris-feeding organisms fill other roles in the community.
Illustration: Russell Shiel
The permanent water source provided by the streams is vital – the water attracts the tree roots, which provide the basis of the community. Water quality can significantly impact on these communities, and this may be polluted by runoff from farms and urban developments which can contain toxins such as oil, grease, rubbish, heavy metal, pesticides and fertilisers.
Water Mouse (Xeromys myoides)
The Water Mouse is small, with grey fur and a white belly. The only known populations of the Water Mouse are in coastal areas of the Northern Territory and Queensland.
The Water Mouse lives near shallow water close to the coast. It forages in mangrove forests for small crabs, shellfish and worms. It is usually active at night (nocturnal) and as the tide goes out, it leaves its nest to forage among mangrove roots, hollow trunks and logs.
The Water Mouse builds large mud nests, up to 60 centimetres high and usually in areas where they can escape the highest of tides. They often use exposed tree roots to form the foundation for the mounds. Water Mice depend on mangrove communities for survival. The mangrove habitat of the Water Mouse is under threat from residential and recreational development. Foxes, feral pigs and cats are also reducing population numbers as they prey on the species.
Tasmanian Giant Crayfish (Astacopsis gouldi)
The Tasmanian Giant Freshwater Crayfish is the largest freshwater crayfish in the world. There are records of specimens reaching more than five kilograms in weight and over 80cm in length. The spiny Tasmanian Giant Freshwater Crayfish is blue to brown in colour and is only found in northern Tasmania, in rivers and creeks that flow into Bass Strait.
The Crayfish are found in flowing and still waters, with adults living in still, deep pools, sheltered beneath submerged logs and overhanging banks. They like well-shaded, clean streams and cooler temperatures.
Overfishing and habitat disturbance, including pollution, have seen the species decline over the last 40 years and it is now listed as nationally vulnerable. A total ban on fishing for this species was introduced in January 1998.
To keep all plants and animals healthy and alive, we need water to be clean and healthy. There are many things that can make our waterways unhealthy. Pollution from factories, litter from stormwater, introduced pests in the waterways, erosion to riverbanks from cattle and land clearing are just some of the many factors damaging Australia's waterways.
If you want to keep our rivers, wetlands and lakes healthy, don't litter on roads, paths or driveways, don't tip milk, oil or fat down the drain, use environmentally friendly products and get your parents to wash their cars on the grass instead of the road or driveway!
And most importantly … spread the word! Tell everyone about how precious water is and how to save it.