These stromatolites, seen in cross section in this fossil, are each just the size of a finger nail. My namesake, geologist Richard T Bell, found them in a rock formation while surveying in remote area of Canada, if I remember correctly, somewhere in the Rocky Mountains.
A stromatolite is a community of micro-organisms forming one layer on top of another. Colonies of cyanobacteria released oxygen into Earth’s atmosphere 3 billion years ago, leading to a mass extinction of anaerobic bacteria but, a billion years later, creating the conditions which would allow multicellular life to appear in the world’s oceans.
From my wildyorkshire.co.uk blog, 19 November 2010:
THESE TINY stromatolites in a fossil from Canada, each about one inch across, were built up layer by layer on the seabed from calcium carbonate secreted by cyanobacteria, also known as blue-green algae. Once thought to be algae, they’re now grouped with the bacteria and, along with archaea, classified as prokaryotes.
Prokaryote cells have DNA but unlike eukaryotes the cells have no membrane-bound nucleus. We’re made up of eukaryote cells but our health depends on a variety of prokaryote cells – the ‘friendly bacteria’ in advertisements for Yakult fermented milk drink – that are active in our digestive systems.
Stromatolites appear right at the start of the fossil record 3,800 million years ago and they’re still with us today, in places like Shark Bay, Australia, where extreme conditions limit competition from other life forms. Stromatolites are often much larger than my pocket-sized examples – the size of a family car, for example.
Blue-green algae can be seen close to home as streaks on the cooling towers of power stations, such as Ferrybridge. The blackish streaks of blue-green algae at Malham Cove (right) gave Charles Kingsley the idea that they might have been made by a chimney sweep’s boy sliding down the face of the cliff, inspiring his story The Water Babies.
Microscopic as they are, the cyanobacteria were crucial in the story of life as they were the first organisms to use photosynthesis, releasing oxygen into the atmosphere. Cyanobacteria contain not only chlorophyll a, a green pigment, but also blue phycobilin, which combine to give the blue-green, almost blackish colour.
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Meeting Richard T Bell, from my wildyorkshire.co.uk diary, 30 March 2007.