It’s not a very long drive from the Overlander roadhouse to the old telegraph station of Hamelin Pool, but the dry shrub-like vegetation makes it a rather monotonous one. The barren landscape is an indication of the hot, dry and windy weather in this remote part of Western Australia, a place where summer temperatures average between 35 and 37 degrees Celsius. Those high temperatures create a very high evaporation rate that turns the shallow waters of Hamelin Pool extremely saline – twice as much as regular seawater to be precise. Under normal conditions this hyper-saline water would be diluted by the flow of fresh or low salinity waters, but in Hamelin Pool this is restricted by very low rainfall and a limited tidal flow.
So what? Is salt water a good reason to stop in such a desolate corner of the world? Well, in Hamelin Pool it is as this environment is rather unique and one of the reasons why Hamelin Pool – and the whole of Shark Bay – is listed as World Heritage. Due to all the saltiness it is the perfect environment for single-celled Cyanobacteria or blue-green algae to flourish as predators such as chitons and snails can’t survive in these waters.
The Cyanobacteria build structures called Stromatolites. On the surface of those structures colonies of up to 3,000 million bacteria form a layer of slimey biofilm, trapping sediments that react to calcium carbonate to form limestone. This is a slow process and to grow to their current mushroom shaped, rock-like dimensions has taken Hamelin Pool’s Stromatolites thousands of years.
Although these structures are between 2,000 to 3,000 years old it is the fact that they consist of living organisms similar to life forms found 3.5 billion years ago that makes them so unique! The colonies of Cyanobacteria use sunlight to convert carbon dioxide into organic carbon and free oxygen, components that are used by other communities of bacteria for the production of new elements and products that are again used by another communities – in this way stromatolites have helped scientists to develop a theory that life on earth depends on interaction rather than competition.
With low tide the stromatolites don’t give the impression they are teeming with life and look more like a field of black lava. The Malgana people, traditional owners of Shark Bay, aptly named Hamelin Pool Boolagoorda meaning black water or black bay, and refer to the rocks as their ancestors. Whatever explanation one prefers, those unique living fossils formed the base for later evolution of higher life forms and are therefore absolutely worth the visit as they provide a glimpse into Precambrian life.