The oldest members of the Coral Coast Crew – living fossils!

Hamelin Pool stromatolites, Shark Bay World Heritage Area, Western Australia (2009).

They may not be as energetic and entertaining as the other members of the Coral Coast Crew, but they are an interesting and important component for evolutionary biology. 

Shark Bay is one of only two places in the world where extant marine stromatolites exist.

Stromatolites are photosynthetic biosedimentary structures of ‘microbial mats’. They are constructed by the entrapment and binding of sediments by cyanobacteria and other microorganisms, which have been formed throughout the earth's evolutionary history.

The world-famous stromatolites at Hamelin Pool, on WA’s Coral Coast, are the only known occurrence of extant stromatolites forming in hypersaline coastal environments.

watch: Stromatolites of Hamelin Pool - Petbur

[This is an older video clip, but has some nice footage and explanation.]

 

Living stromatolites, Shark Bay, Western Australia - Paul Copper (2013) 

These halophilic ("salt-loving") Archaea have adapted to living in extremely hostile environments. Halophilic Archaea are chemoorganotrophs and belong to the class Euryarchaeota. Halophilic Archaea are of particular interest as they are astonishingly robust organisms, able to survive being desiccated into a crust of solid salt, resulting in extremely high longevity (millions of years and possibly indefinite!) entrapped in salt crystals. Stromatolites grow successfully and undisturbed at Hamelin Pool because the sea water is twice as saline (as usual sea water) due to partial isolation by a sandbar across the entrance of the bay and the rapid evaporation from its shallow water. Halophilic Archaea thrive in concentration of salt even five times greater than that of the ocean (higher than those used in any food pickling processes!). They actually require high salt for growth and they are adapted to environments which have little or no oxygen available for respiration.

·         Fun Fact! The Shark Bay World Heritage area has the Westernmost Point of Autstralia – Steep Point, Western Australia (26° 09' 5" S113° 09' 18" E).

How microbialites form, Government of Western Australia (2013).

These ancient structures are monuments of what life on Earth was like 3.5 billion years ago as they contain living microbes (that build the stromatolites) similar to those found in 3,500 million year old rocks - the earliest record of life on earth! The stromatolite structures which are found to be up to a metre high are believed to be hundreds to thousands of years old as they grow at a maximum of 0.3mm per year.

Hamelin Pool is home to the most abundant and diverse examples of living stromatolites in the world. Several halophilic archaea, belonging to the genus Halococcus, have been identified at the Coral Coast location, preserved in the geological record for over 3 billion years. As such, these stromatolites are considered ‘living fossils’ which provide a record of local environmental changes. The Coral Coast Hamelin Pool stromatolites are considered the oldest and largest ‘living fossils’ part of the Earth's evolutionary history.

Watch: Stromatolites, proof of Life's Origin HD- Western Australia

[There’s quite an interesting introduction into the Earth’s history leading up to the stromatolites 

(just under 3 minutes into the video if you wanted to skip to it).]

Watch: Why do we care about stromatolites - Virtual Field Trips

BIBLIOGRAPHY:

Goh, F., Leuko, S., Allen, M.A., Bowman, J.P., Kamekura, M., Neilan, B.A. & Burns, B.P. (2006) Halococcus hamelinensis sp. nov., a novel halophilic archaeon isolated from stromatolites in Shark Bay, Australia, International journal of systematic and evolutionary microbiology 56 (6), 1323-1329.

Papineau, D., Walker, J.J., Mojzsis, S.J. & Pace, N.R. (2005) Composition and Structure of Microbial Communities from Stromatolites of Hamelin Pool in Shark Bay, Western Australia, Applied and Environmental Microbiology 71 (8), 4822-4832.

Renee, C. & Wandersee, J. (2013) STROMATOLITES, The Science Teacher 80 (2), 60.

Paul Copper (2013) image: Living stromatolites, Shark Bay, Western Australia. Australian Institute of Marine Science, <http://coral.aims.gov.au/info/reefs-palaezoic.jsp>.

Government of Western Australia (20013) image: How microbialites form, Government of Western Australia <http://www.dmp.wa.gov.au/5257.aspx>.

Shark Bay World Heritage Area (2009) image: Hamelin Pool stromatolites, Shark Bay World Heritage Area, Western Australia <http://www.sharkbay.org/stromatolites.aspx>.