Some notes on Urschleim and the Origin of Chalk


A chalky suspension of coccolithophores, chalk makers

A chalky suspension of coccolithophores, chalk makers

Coccolithophores are single cell microscopic organisms that live in large numbers throughout the sunlight zone  of the Earth’s oceans. Unlike other types of phytoplankton, these organisms surround themselves with a rigid microscopic armour made of calcium carbonate. This exoskeleton comprises of at least 30 small hubcap shaped calcium carbonate scales known as coccoliths.   Whilst coccolithophores are microscopic they have had a dramatic impact on our planet. As these minute organisms live and die in their trillions, they sink to the ocean’s floor where over time their calcium carbonate  plates form rocks such as chalk and limestone. . Over geological time, these organisms have removed significant amounts of carbon dioxide from the atmosphere. Today, it is estimated that coccolithophores deposit more than 1.5 million tons of calcite a year, making them the leading calcite producers in the ocean. As the concentration of carbon dioxide it the Earth’s atmosphere increases, and its oceans become acidified, it has been predicted that coccolithophores will be less able to generate calcium carbonate and this may have global implications for the carbon cycle.

Thomas Henry Huxley (“Darwin’s bulldog”) was one of the first to examine to detect coccoliths within marine sea muds and was the first to use the term “coccolith”. However, he initially thought that he had discovered a new organic substance and believed it to be a form of primordial matter, the source of all organic life, after Haeckel had theorized about Urschleim (primordial slime).

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