Stromatolites and Thrombolites of Western Australia

Are these ordinary beach rocks kids so easily skip across or ancient living life forms?

Normally they would be common beach rocks revealed by the out going tide but these are tiny living organisms that are so microscopic, that individually, the human eye can not see them. They range in size from 1-10 micrometres (millionths of a metre).

Not only are these seemly boring grey blobs alive but they allow us to view through the window of time. Nothing else is living today from the earliest of times. These stromatolites living now are very similar.

Cyanobacteria have changed our environment more than any other living thing by giving Earth oxygen.

These Fossilised stromatolites (below) are from the Warrawoona formation at North Pole near the coast in the Pilbara region in Western Australia. They are dated at 3,460 million years old and are the oldest life on earth. They are seen here as a cross section. Please click on the photographs to see them larger. There are four different kinds of filamentous which are thread like microfossils. These Fossilised cells resemble the prokaryotic cells that build the stromatolites today. These rocks at the north pole in the Pilbara are mostly volcanic rocks and sedimentary rocks.

Back when these fossils were living this area was a shallow sea. This was a tough time to be alive, there was very little oxygen and and no ozone layer to absorb the deadly ultraviolet radiation.

They were photographed at the Western Australian Museum.

Stromatolites are;

in the Monera Kingdom - true bacteria and Cyanobacteria
a community, they need each other for survival.
a single celled organism (hey, don't knock their intelligence remember how long they have managed to survive with out destroying themselves).
together they build the dome like structures of sediment.
are also called microbialites.
they have DNA.
they have no nucleus.
they have chlorophyll
they photosynthesize. They take carbon dioxide and water to produce carbohydrates, and in doing this they liberate oxygen into the atmosphere which all living life forms need.
They grow extremely slowly, about 0.5-1mm a year.
need carbon and bicarbonate ions for their constructions.
The outside of the stromatolite is not living, that is the protective crust.
they were very common in the early Phanerozoic time to the Precambrian time. However they haven't been common through all of time.
Even in the one place like at Hamlin Pool in Shark Bay the stromatolites will have different internal structures depending on where they are in relation to the shore line due to the different water depths.

The stromatolites closer to shore are called 'pustular-mat' and are mainly formed by the coccoidal cyanobacterium Enotophysalis. These stromatolites are unlayered or unlaminated and have a poorly defined internal structure and are found in the inter-tidal zone.
The middle group of stromatolites are called 'smooth-mat' which are made with the cyanobacterium Schizothrix. These are layered or laminated with a smooth outer surface and have a well-defined internal texture. These are found in the lower inter-tidal to the upper sub-tidal zones.
The stromatolites that live in the deepest water of about 3.5m are called 'colloform-mat' and can grow up to 1m high. They are a complex community including cyanobacteria Microcoleus and Phormidium and some algae are found in this area. They produce mucus that traps the sediment and may make these stromatolites different to those of ancient fossils. These are found in the sub-tidal zone.

How do Stromatolites build their domes?

The uppermost layer of each stromatolite is a sticky mat of cyanobacteria. Over time, debris sticks to the cyanobacteria, cutting it off from sunlight which is needed for photosynthesis. In response, the cyanobacteria grow upward through the debris to form another layer and so on.

How do they reproduce?

Each individual one simply divides itself. The DNA uncoils and duplicates itself into the new cell. This means they are the same but on rare occasions mutations happen where the DNA wasn't an exact duplicate and so changes the new cell.

How did they produce so much oxygen?

Well if you were around for 4 billion years on your own with no enemies (except for meteors in the early days) and nothing to do but divide yourself, and if there are plenty of you, the job gets done.

How have they survived through 4 billion years?

Well living alone for such a long time has its advantages, nothing to eat you or to make a home out of you. Those stromatolites that grew or still grow in sea water that is twice as salty as normal sea water also have little competition even today. How did they survive the atmosphere of little oxygen and no ozone layer? I don't know but probably due to their simplicity, when you're only one cell how much can go wrong.

There are some organisms that weren't that thrilled with the arrival of the cyanobacteria though puffing out all this oxygen, they either died or hid in places that the oxygen couldn't reach.

Shark Bay Stromatolites

These Stromatolites here are not fossils they are alive and growing at Shark Bay located approx 600km north of Perth on the coast in the Gascoyne region. Living Stromatolites are also at Lake Clifton and Lake Richmond south of Mandurah and Rockingham, Lake Thetis southeast of the Cervantes, Rottnest Island off Perth and Pink Lake in Esperance in the lower southwest of WA.

Photographs by Mary Heslan

The sea water around the Shark Bay stromatolites can be up to twice as salty than normal sea water. Not all stromatolites grow in highly salty water, some grow in freshwater.

4,000 years ago sea grass and bivalves lived here in this area.

Lake Thetis stromatolites

Located 3km southeast of the Cervantes/Pinnacles in the Wheatbelt/Heartlands region.

These photographs were taken in November

This is a saline lake where the water is approx 1.3 times more salty than normal seawater. The ground water is rich in calcium and bicarbonate is released into the lake for the limestone structure of the stromatolites. This happens by an underground stream.

You can see the stromatolites around the lakes edge. These stromatolites also trap and bind the sediments.

These stromatolites are approx 1,200 years old. The largest domes are 1m wide. They are layered and have internal branched columns up to 10cm high which is rare now but was common in Precambrian rocks.

Here at Lake Thetis we saw birds using the lake such as Dotrels and Black-winged Stilts running along the lakes edge.

What's the Diff?

What is the difference between Stromatolites and Thrombolites?

This is not an easy question to answer. Looking at the physical outside appearance there doesn't seem to be any difference. Different things make this difficult to answer such as whether or not the stromatolites are younger or from the Phanerozic time, there are around 2000 species of cyanophyta and more research on a greater variety of stromatolites will be done into the future hopefully making these tiny marvels easier to understand.

Stromatolites...

Thrombolites...

are thinly laminated organosedimentary structures that are generally believed to be or have been formed by a variety of microbial organisms (Hoffman, 1973; Ginsburg, 1991).

Stromatolitic laminae probably form by a combination of trapping and binding of sediment by the microbial organisms and by direct precipitation of carbonate minerals from the water column by the organisms (Hoffman, 1973).

Stromatolitic laminae typically are convex-upward or concentric, giving the structure a form similar to a head of cabbage.

are cryptalgal structures that do not have a laminated fabric structure. Instead, thrombolites exhibit a macroscopic clotted fabric (Aitken, 1967; Kennard and James, 1986).

Millimeter- and centimeter-size clots of microbial origin are separated from one another by patches of mud to sand-sized sediment. The clots are generally thought to represent microstructures formed by the insitu calcification of calcareous algae and cyanobacterial communities (Aitken, 1967; Kennard and James, 1986).

Text; Go here to try and understand more about Stromatolites and Thrombolites

http://www.winona.edu/geology/
paleo/labs/microbialLab.htm

Go Here to see images of Thrombolites http://mgg.rsmas.miami.edu/groups/geomic/
STROMATOLITE/thro.html

I guess for now they will remain one of life's little mysteries!

Lake Richmond Thrombolites/ Stromatolites Located 1km south of Rockingham south of Perth. This small lake is 1km long and approx 600m wide and 15m deep. This is a freshwater lake. The Thrombolites/ stromatolites here are elongated domes.

Little research has been carried out on these Thrombolites/ stromatolites. They grow in calcium carbonate which comes through the ground water from the surrounding sand dunes that are mainly composed of calcium carbonate sands. It didn't appear that these Thrombolites/ Stromatolites were in very good condition and there was no access to see them up close. On the day I visited I saw pelicans, musk ducks, eurasian coots, pacific black ducks, black swans, little grebes and black-winged stilts. There were reeds around the lakes edge. These photographs were taken in early March.
Lake Clifton Thrombolites/Stromatolites Located in the Yalgorup National Park on the Old Coast Rd south of Mandurah approx 100km south of Perth in the Peel region. We will call these either thrombolites or stromatolites. This coastal lake is 21.5km long by 1km wide and is a shallow lake at only 1-3metres deep. There is a reef of stromatolites 30m wide and 5km long. The stromatolites are from 40cm-1m wide. Here in the photos below you can see the stromatolites above the water as the lake level drops in summer. The water here is less salty (brackish water) than normal sea water. Even though this lake is very close to the sea it is not fed by the sea. It receives its water from rainfall and an underground water supply. As with some of the other stromatolites the ground water is critical to their development as it is the source of carbonate and bicarbonate. These stromatolites are cyanobacterium scytonema.

These stromatolites have competition for their survival here at this lake with crustaceans and mollucs grazing on them. The only birdlife I have seen here at this lake was a Welcome Swallow. Not to far from the lakes edge frogs were heard in a water catchment. Oblong/Long necked turtles also live in Lake Clifton.

Rottnest Island Stromatolites

There are a few salt lakes on Rottnest Island off Perth WA. In a few places at some of these lakes such as the Government House Lake the algal cyanobacterial that covers the lake with benthic microbial mats develop into small domed stromatolites. They are found in shallow water where nodular branching columns and smooth domes occur. These may grow at a rate of 1.5mm per year.
There is a lot of limestone on and around Rottnest Island.

On Rottnest there are Quokka's that come down to the salt lakes to eat the vegetation such as this Berrysalt bush.

I have not seen these stromatolites yet.