Leaving Fremantle and Thrombolites

My second morning in Oz and a breakfast fuel-up of coffee and smoked salmon bagel at Gino's Cafe, Fremantle, before the long drive to Quinninup


When we stopped for fuel and air I was amused at this man's inept attempts at filling the wheel chair tyres with air. My driver was just impatient.

Lake Clifton is one of the few places in the world where microbialites, "living rocks", grow. (Microbialites are one of the earliest forms of life on earth). Lake Clifton is the largest lake-bound microbialite reef in the southern hemisphere

Thrombolites are the most common form of microbialite in Lake Clifton. They are formed by a variety of micro-organisms. As the micro-organisms photosyntthesise they draw calcium carbonate from the lime-rich lake water to form limestone mounds

(Stromatolites form in a different way, mats of gelatinous slime trap seiment particles, similar to the way in which the sticky hairs of sundews catch flies.)

Microbialites grow at about 1mm per year

Thrombalites are characterised by an internally granular texture whereas stromatolites have a stratified structure.

The Lake Clifton thrombolites represent extant examples of thrombolites that were common 600 million years ago. Fossil counterparts are found today in the Amadeus Basin in the Northern Territory where ancient shorelines once existed.

Microbes involved in thrombolite and stromatolite formation may have been responsible for the oxygen production which enabled life as we know it to colonise the planet.

The tragedy that is happening here is that the massively increasing suburbanisation of the Swan Coastal Plain of Western Australia is causing the eutrophication of Lake Clifton. This eutrophication is causing the algae which is smothering the thrombolites and killing them. (Eutrophication in lakes and rivers is the excess nutrient caused by run off from lawn, garden and agricultural fertilisers which gives rise to phytoplankton, or algal bloom.) The sediment and algae smothering the thrombolites can be seen in the pix.

(I've pinched some of the text from the WA DEC notice board at Lake Clifton)