Along the shore of Lake Clifton, just south of Mandurah in Western Australia, is a reef of smooth, round structures covered by shallow, brackish water. The wind stirs up sea foam which gathers around them and there’s an eerie feeling that something ancient exists here.
They look like rocks but the reef is actually composed of thrombolites – the creation of micro-organisms called cyanobacteria. Their ancestors were among the first forms of life on Earth during the Archaean eon, 3.8 billion years ago. These microbes create a film of calcium carbonate during photosynthesis and gradually, through a process of clotting, the thrombolites are formed. It is only the very outside layers that support these tiny living organisms and depending on water levels they can be exposed, or like the day we were there in mid-winter, completely underwater.
Once the oceans of the Earth were full of thrombolites but now Lake Clifton is one of only two places in the world where living examples occur and measures have been taken to ensure their protection. It’s a short walk through the bush to the edge of the lake and on to the specially built boardwalk, which allows visitors to see the thrombolites up close without causing any damage.
In geological terms these thrombolites are in their infancy at just 2000 years old. Let’s hope they endure for at least another 2000 years.