Assemblages of plants and invertebrate animals of tumulus (organic mound) springs of the Swan Coastal Plain facts for kids

Tumulus Springs of the Swan Coastal Plain are very special natural areas in Western Australia. They are home to unique groups of plants and tiny animals that live together in what scientists call an ecological community. These amazing places are also known as Mound springs of the Swan Coastal Plain. The springs create small, natural mounds of peat and sand. These mounds were once common along the edge of the Gnangara Mound aquifer, where sandy soil meets heavier clay. Sadly, these communities are now critically endangered, meaning they are at very high risk of disappearing forever.

What are Tumulus Springs?

At the edge of the Gnangara Mound, where heavy clay soil meets sandy areas, water from underground aquifers comes to the surface. This creates bogs and swamps. On the Swan Coastal Plain, near the Darling Scarp, this also forms permanent springs. Over time, these springs build up mounds of peat and sand. These mounds are filled with special plants and tiny animals. As plants continue to grow, they create unique small homes, called microhabitats, for many different species. The constant flow of water from deep underground helps these mounds grow bigger by pushing more material to the surface through the layers of peat.

Who lives in these springs?

The animals found in these springs include very old types of invertebrates. These are often unique to these remaining mounds, meaning they aren't found anywhere else. Some of these species are "relict Gondwanan," which means they are survivors from a time when Australia was part of a supercontinent called Gondwana!

The plants around the springs include flooded gums (Eucalyptus rudis), bracken fern (Pteridium esculentum), and various rushes. These plants are often leftovers from past climates in this bioregion. Today, they are usually only found much further south.

Tiny creatures of the water

Many of the animals living in these springs are highly adapted to life in permanent water. This special habitat might even help them survive changes in climate. Many of these species are found only in the tumulus mounds of the Swan Coastal Plain.

Tiny creatures like mites, ostracods (small crustaceans), nematodes (roundworms), Cladocera (water fleas), copepods (tiny crustaceans), oligochaetes (segmented worms), tardigrades (water bears), Turbellaria (flatworms), and many types of insects are found in most of the three remaining springs.

Special aquatic mites have also been found at these mounds:

• Aturidae: Notoaturinae, gen. nov. sp. nov. - found at Bullsbrook
• Anisitsiellidae: Anisitsielides sp. nov. - found at Muchea
• Crangonyctoid Amphipods: Paramelitidae, gen. nov. sp. nov. – found at Ellenbrook

Plants that make up the habitat

The plants are very important for keeping these communities alive. They create the structure of the habitat.

• Tall trees: You can find Banksia littoralis, Melaleuca preissiana, and Eucalyptus rudis.
• Medium and low plants: These include vascular plants like Agonis linearifolia, Astartea fascicularis, Cyclosorus interruptus, and the fern Pteridium esculentum.
• Non-vascular plants: These are simpler plants like Lycopodiella serpentina (bog clubmoss), Riccardia aequicellularis, Jungermannia inundata (from the Jungermanniaceae family), Goebelobryum unguiculatum, and Hyalolepidozia longiscypha (from the Lepidoziaceae family).

Where are these special places found?

These springs were once common in a narrow strip between Guildford and Muchea. But now, only three remain, covering a total area of just eight hectares. You can find them at Ellenbrook, Bullsbrook (known as Kings Mound Spring), and one near Muchea.

Why are they in danger?

Most of these unique communities were destroyed when land was cleared after people settled in the area. Human activities have caused a huge loss, reducing the number of mound spring communities by 97% since settlement. Many were destroyed by building dams and filling in land for farming. Later, housing developments caused even more loss.

The mound springs are now critically endangered. The three remaining communities are protected by either the state government or special urban development reserves. All the plants and animals living in these springs face the same threat of extinction because their environment is changing.

Here are some of the main threats:

• Changed fire patterns: Fires that are too hot or happen too often can damage the springs.
• Water use: Taking too much water from the underground aquifers directly threatens the springs, as they rely on this water.
• Cattle grazing: Cows eating plants and trampling the ground directly harm the species. Their dung also helps invasive weed species grow.
• Weeds: Introduced plants like Isolepis prolifera and Pennisetum clandestinum are a big problem. They push out the native species. Grassy weeds also increase the risk of fire, and woody weeds drink a lot of the spring's water.

All these threats together reduce the variety of life, known as biodiversity, and continue to push these special communities towards extinction. All three identified mound springs and their species are eligible for special protection under state laws.

See Also

• Natural history of Western Australia
• Protected areas of Western Australia
• Swan Coastal Plain