Recently I was lucky enough to survey a mound spring in north Queensland with Ewamian traditional owners and a group of freshwater ecologists. Looking through the eyes of people from different backgrounds proved the springs have many stories to tell.
In broad terms, springs are places where water from underground comes to the surface. Western knowledge of springs in Queensland is limited and relates mainly to springs associated with the Great Artesian Basin (GAB) – a vast underground aquifer system feeding many of Australia’s springs.
A survey of GAB springs in Queensland between 1995 and 2002* identified 730 active springs and another 372 inactive springs. Talaroo#, the spring I visited, is thought not to be part of the GAB system – sourcing water from a yet to be identified aquifer.
On my first visit to the springs I didn’t think too much about the large mound structure in which the hot water flows and bubbles through a series of vents. Through the eyes of an expert in cyanobacteria (or blue-green algae – bacteria that obtain energy via photosynthesis) the mound is a conglomerate of past life.
While the term ‘mound springs’ is commonly used, in reality only 18% of surveyed active springs in Queensland had a mound greater than 0.2 m high*. Mounds can develop via a number of processes. At Talaroo it is through the accretion of minerals in the water (calcium carbonate) as “travertine”. The conditions at Talaroo mean that cyanobacteria colonise the surface and when they die their structures are preserved in the crust giving it a porous appearance.
But blue-green algae aren’t the only organisms whose bodies are being incorporated into the mound.
Looking through the eyes of a bug expert an “insect graveyard” was discovered. At first we noticed the accumulation of dead dragonflies washed up like flotsam on the edge of one of the spring pools. Closer examination showed bodies in advanced stages of crystallisation. Like stone jewelry, these encrusted insects will also one day become part of the mound.
But it wasn’t all death and crystallisation. Surveys of the small creeks flowing out of the springs showed temperatures cooling with distance from the springs. Insect life, while not abundant was found. Lab work will reveal whether Talaroo, like other mound springs, supports any previously undescribed fauna such as snails.
While the drop off in creek life was expected as water temperatures rose, the final discovery took everyone by surprise. Closer observation of the spring pools revealed animals were living there as well. In water of around 45 degrees teams of microcrustacea (ostracods) were found swimming frantically. Time will tell if they are something new to science.
Ewamian people regard the springs as a story place. They have observed changes in water levels that follow the lunar cycle. I can’t help but think Talaroo has more stories to tell us all.
*The full article on which this piece is based is: Spring wetlands of the Great Artesian Basin, Queensland, Australia. By: R.J. Fensham and R.J. Fairfax. Wetlands Ecology and Management, 2003, 11, 343–362.
# Talaroo hot springs are not open to the public at the time of writing. The work done will help the Ewamian traditional owners develop an appropriate management plan for the springs.