i.e. sand, crushed shell etc. are trapped by the sticky bacteria, to become cemented with calcium carbonate produced by the bacteria, thereby building up the stromatolite structures. Some structures are pillars up to high and have taken thousands of years to grow. In the Marble Bar area of Western Australia there are fossil stromatolites approximately high and diameter. These are estimated to be over three billion years old. Typical growth is about per year. There are three basic types of stromatolite, the sub-tidal (always under water) columns and the inter-tidal (exposed to air and sun during low tides) anvil or mushroom shapes depicted in most pictures. Algal mats form in the inter-tidal region and appear as areas of flat black mud flats but are actually living stromatolite. At Hamelin Pool there is an interpretive boardwalk for tourists to venture out and examine the stromatolite structures. This is the only access area for the general public because of the fragile nature of the environment in the Hamelin Pool. The Hutchinson Island and the Pelican Island are located within the nature reserve. Telegraph station At the Historic Hamelin Pool Telegraph Station built in 1884 and Historic Old Post Office first built in 1886 now the local Community Post Office/Public Phone Box. The museum showing information on the growth of stromatolites and includes what is the only stromatolites living in captivity (in an aquarium) in the world. The museum also covers the building and operation of the Historic Telegraph Station back to the 1880s. References Further reading (1994) Shark Bay marine reserves draft management plan : Shark Bay Marine Park, Hamelin Pool Marine Nature Reserve Department of Conservation and Land Management for the National Parks and Conservation Authority. Perth, W.A : CALM for the National Parks and Nature Conservation Authority. "Shark Bay marine reserves draft management plan 1994"—Cover. Thomson, Carolyn (1997) Discovering Shark Bay Marine Park and Monkey Mia Como, W.A. Department of Conservation and Land Management. Western Australia & Bancroft, K & Davidson, J (2002). In Field survey of marine ecological communities in Shark Bay Marine Park and Hamelin Pool Marine Nature Reserve (18–29 March 2002) : Marine Management Support, Shark Bay. Dept. of Conservation & Land Management, Marine Conservation Branch, Fremantle, W.A External links Hamelin Pool Marine Nature Reserve Nature reserves in Western Australia Natural pools Shire of Shark Bay DIWA-listed wetlands