Thrombolites of Lake Clifton
Rock-like structures at the edge of Lake Clifton, built by micro-organisms too small for the eye to see.
Best viewed large.
Rock-like structures known as thrombolites can be seen on the edge of Lake Clifton. Like the famous stromatolites of Hamelin Pool, in Shark Bay, the thrombolites are built by micro-organisms too small for the human eye to see. Within the structures of Lake Clifton, are living communities of diverse inhabitants with population densities of 3000 per square metre! Lake Clifton is one of only a few places in Western Australia where living thrombolites survive. These peculiar structures live on the eastern edge of the lake and are most easily seen in March and April. Microbial mounds, which are the remains of thrombolites, can be seen at nearby Lake Preston.
The thrombolite-building micro-organisms of Lake Clifton resemble the earliest forms of life on Earth. The discovery of modern examples helped scientists to understand the significance of micro-organisms in the environment and unravel the long history of life on Earth. These organisms were the only known form of life on Earth from 3500 million to 650 million years ago. The thrombolites and stromatolites they constructed dominated the clear, shallow seas of this period and formed extensive reef tracts rivalling those of modern coral reefs. Similar organisms, for instance, helped to form the rich iron-ore deposits of the Hamersley Range, in the Pilbara's Karijini National Park, some 2000 million years ago. At this time oxygen made up only one per cent of the atmosphere. When there was no more iron to precipitate, the free oxygen leaked into the atmosphere until it formed 21 per cent of atmospheric gases.
Today living examples of these once completely dominant organisms are restricted to only a few places. So why do thrombolites grow at Yalgorup? Scientists have suggested it is perhaps because Lake Clifton is associated with upwellings of fresh groundwater that are high in calcium carbonate. The micro-organisms living in this shallow lake environment are able to precipitate calcium carbonate from the waters as they photosynthesise, forming the mineralised structure that is the thrombolite.
The significance of thrombolites and stromatolites to science is inestimable but they are very fragile and can be degraded by visitors walking over them. To protect the thrombolites, an observation walkway has been built to minimise any impact from visitors wanting to see these fascinating structures.