Rare, ancient stromatolites discovered in Tasmania
These large grey mounds, known as stromatolites are said to be the oldest record of life on earth, with only a few colonies still in existence. But now scientists have discovered that they're thriving in the Tasmanian wilderness.
RESEARCHERS FROM the University of Tasmania (UTAS) and the Department of Primary Industries, Parks, Water and Environment (DPIPWE) have discovered a small deposit of rare micro-organisms known as stromatolites, which, when compounded, typically resemble large, grey mudcakes, in the Tasmanian wilderness. But despite their lacklustre appearance, stromatolites are extremely rare and are only found in a few localities around the world.
"We weren’t specifically looking for stromatolites or microbial mats in general," says Bernadette Proemse, a Senior Research Associate at the School of Biological Sciences at the UTAS. Rather, the group made the discovery while they were surveying a remote peat-bound karstic wetland in Tasmania’s south west, which Bernadette explains is a special kind of ecosystem depending on mineral rich groundwater discharge.
"Our discovery adds to our understanding of stromatolites because peat-bound karstic wetlands are unlike all other reported habitats for stromatolites. These wetlands are not saline or geothermally heated like stromatolite habitats in some other parts of the world," says Rolan Eberhard, a researcher from the DPIPWE. "Prior to this discovery, stromatolites were not know from Tasmania except as ancient fossils," he adds.
Bernadette says that the water chemistry of the groundwater that discharges at the spring mounds hosting these stromatolites is a key factor for the suitability of the site.
"The calcium rich water is super-saturated with respect to calcite, and grazing metazoans such as snails are challenged by calcification of their shells. The stromatolites were in most parts not submerged by water, suggesting that the high amount of rainfall at this site contributes to the suitability of this habitat for stromatolite growth."
It's estimated that stromatolites are the oldest record of life on Earth, first emerging around 3.5 billion years ago. According to Bernadette these micro-organisms were abundant in the fossil record until multicellular life was formed in the Cambrian era, after which they've suffered huge declines. Now, the most well-known living stromatolites in Australia are the shallow marine stromatolites in Shark Bay in Western Australia.
However, the discovery of this new colony of stromatolites has given the researchers new hope. "We were very excited because living stromatolites are believed to be rare... stromatolites may colonize a much broader range of freshwater environments than previously thought, and that stromatolites may be more common than presently recognized," says Bernadette.
Stromatolites in Shark Bay in Western Australia. (Image Credit: Wikimedia)
Bernadette and her co-author John Bowman, a biologist from UTAS, says that when stromatolites first evolved, Tasmania did not exist in it’s current shape and location.
"The Giblin Spring stromatolite community in Tasmania is very unique compared to other living stromatolites and could have evolved in its current form only in the south-west of Tasmania, unless a similar system is found elsewhere in the world. The microbes making up the community could have potentially evolved over millions of years," they say.