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Stromatolites and Lake Thetis, Cervantes WA 6511, Australia – part 1 of 2

By on August 28, 2015 in Australia

On thing I was really looking forward to on my trip to Western Australia was visiting Lake Thetis in Nambung National Park, Cervantes, to look at some Stromatolites.

When I told a number of my friends that I was really looking forward to seeing the Stromatolites I was typically greeted with a blank look, and the question “what’s a stromatolite?”, and once I had explained there was usually a followup question of “why?”. I’ll explain below…..

Stromatolites are descendants of some of the earliest lifeforms on Earth dating back to about 3.5 billion years ago, and this, to me, makes them particularly interesting. Plus, until surviving colonies were found in Western Australia (Sharks Bay and Lake Thetis), Brazil, Mexico and the Bahamas, they were thought to be extinct. They are living fossils (even if they do look like lumps of rock).

Stromatolites are important for the evolution of all life on the planet as they were some of the first organisms to produce oxygen.

The lake is a protected conservation area and you approach the stromatolites long a 300 m boardwalk that runs over a ‘blister mat’ of bacteria in the top layer of sediments. These bacteria produce oxygen that form ‘sand bubbles’ on the surface, hence the formation of a ‘blister mat’ (also called a crenulate mat). As you can imagine the mat is very delicate, hence the boardwalk.

One of the reason that the Stromatolites are in the lake, and only found at a few locations around the world, is because they need very specific conditions for the cyanobacteria to produce the rock-like platforms seen in the above photos. The lake need to be free of predators so that the bacteria can grow undisturbed, and also relatively calm. Lake Thetis is predator free, and calm. It is free of predictors as the lake is 1.5 times more salty than the sea, and it is so salty and calm as it is not connected to the nearby sea.

It is amazing to think that these organisms have been growing for 3,500 years in the lake.

And although I keep writing about Stromatolites the lake actually contains both Stromatolites and Thrombolites.

The Stromatolites are built up in layers, whereas the Thrombolites have a more clotted structure.

As the cyanobacteria bacteria grow (and it is the wet dark parts of the Stromatolites in which growth occurs) they bind calcium carbonate in to the surface of the Stromatolites.

FourSquare: Lake Thetis

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