Hamelin Pool - Stromatolites
In the hyper-saline water of Hamelin Pool at the base of Shark Bay's eastern gulf the rocks aren't quite what the appear to be. They are living things, Stromatolites, which are the oldest living organisms on the planet. Some scientists believe they were the first living things on mother earth. .
Hamelin Pool is the location of the best example in the world of living marine stromatolites. The water of Hamelin Bay is twice as saline as usual sea water because of a bar across the Bay's entrance and rapid evaporation from the shallow water. Most living animals, which feed on the bacteria and algae of which stromatolites are composed, cannot tolerate such saline conditions. As a result stromatolites can grow here successfully, undisturbed. Most stromatolites are extremely slow growing. Those in Hamelin Pool grow at a maximum of .3mm a year, so those which are up to a metre high are hundreds if not thousands of years old.
Stromatolites are formed through the activity of primitive unicellular organisms: cyanobacteria (which used to be called blue-green algae) and other algae. These grow through sediment and sand, binding the sedimentary particles together, resulting in successive layers which, over a long period of time, harden to form rock. For at least three-quarters of the earth's history stromatolites were the main reef building organisms, constructing large masses of calcium carbonate.
However their most important role in the history of the earth has been that of contributing oxygen to the earth's atmosphere. The organisms which construct stromatolites are photosynthetic. They take carbon dioxide and water to produce carbohydrates, and in doing this they liberate oxygen into the atmosphere.
When stromatolites first appeared on earth about 3.5 billion years ago there was little or no oxygen in the atmosphere. It was through the oxygen-generating activity of stromatolites that other animal life on earth was able to develop. Conversely, it is believed that the decline in numbers of stromatolites is related to the evolution of animals that consumed cyanobacteria and algae.
Stromatolite fossils are evidence of the earliest life on the earth. Western Australia perhaps has the best stromatolite fossils, giving a record through the eons of time. Fossils of the earliest known stromatolites, about 3.5 billion years old, are to be found near Marble Bar in the Pilbara.
Evidence of the beginnings of life on Earth can be found in saline waters of Hamelin Pool - the famous stromatolites. Hamelin Pool Marine Nature Reserve is one of the only two places in the world where living marine stromatolites are known to oocur and it is the only place where they can be easily seen from shore. Microscopic organisims - invisible to the human eye - concentrate and recycle nutrients which combine with sedimentary grains to form domes of rock - like materials known as stromatolites.
Hamelin Pool gives an indication of what the earth may have looked like 3.5 billion years ago when stromatolites were widespread. Because of their range and numbers it is a place of great interest to botanists and geologists alike. A jetty has been constructed allowing the stromatolites to be viewed without doing them irreparable damage.
It's a humbling thought that all life on this planet could have started from something so simple as the blue-green algae which created these rocks millions of years ago.
amelin Pool Telegraph Station and Shell Block Quarry
Hamelin Pool Telegraph Station was built in 1884 on the Perth to Roebourne telegraph line. The original building is now a historic museum. The nearby quarry has provided compacted shell blocks for use in the building of station homesteads, civic buildings and the landmark Old Pearler restaurant in Denham. For access to the quarry enquire at Hamelin Pool Caravan Park. (Stromatolites - listed under Shark Bay Marine Park). There is an interesting museum and tearooms at the near by Hamelin Pool Telegraph Station.