Thursday, 7 March 2013

100 Species, Number 7: Coccoliths

David North, Head of People and Wildlife

I don’t suppose many readers will have heard of coccoliths or coccolithophores to give them their full name, let alone the species Emiliana huxleyi. Yet this species, and its coccolithophore friends and relatives, might even deserve first place amongst the species that have made Norfolk. 

I have never seen a living E. hux. Though both you and I have probably swum amongst them and have certainly walked miles over their dead remains. So how can this be? One of the commonest species in the world, very beautiful (try googling E hux images), yet almost unknown. Well E hux suffers two problems for any species wanting a high profile, its marine and its tiny – so doesn’t rank highly in the cute and cuddly stakes. 

Thomas Huxley, friend of Charles Darwin, gave a lecture to working men in Norwich in 1868 titled ‘On a piece of chalk’. The lecture starts, ‘If a well were sunk at our feet in the midst of the city of Norwich, the diggers would very soon find themselves at work in that white substance almost too soft to be called rock, with which we are all familiar as ‘chalk’. Huxley goes on to describe how a friend of his Captain Dayman, had been ordered by the Admiralty to take samples of the sea-bed bottom between England and America as part of the work to lay the first trans-Atlantic telegraph cable in 1853. Thomas Huxley was sent these samples and examining them with a microscope realised that the structures he saw, were clearly the remains of living creatures, and identical to those beautiful spherical structures, coccoliths, that he had also seen in chalk rock. His Norwich lecture, still available on the internet, is a highly readable work of genius which explains how chalk is actually the remains of once living marine creatures which still roam our seas today. As Huxley said, ‘A great chapter of the history of the world is written in chalk’.

The chalk, probably more than one thousand feet thick, which lies under the North Norfolk house where I am writing this, is composed of uncountable billions of small white globules which have been described as like snowballs made from brittle paper plates. A description which of course fails to capture the beautiful, geometrical complexity of these structures.

So E hux and other coccolithophores are actually forms of single celled marine algae which build their tiny skeletons from plates of calcite. These calcite plates, coccoliths, sink to the bottom of the sea, not just when the organisms die, but are also shed as they multiply asexually or simply grow. This process, which has formed the chalk beneath our feet in Norfolk, continues today and it’s estimated that more than 1.5 million tons of calcite a year fall to the ocean bottoms from their activity each year.

Thomas Huxley didn’t know the age of the chalk in Norfolk, or how long it took to produce it, though he pioneered the research and thinking on how these geological processes work and are connected to living systems. We now know that the chalk that is the bedrock of Norfolk was laid down between 100 million years ago and 60 million years ago when as Huxley rightly deduced in his Norwich working men’s lecture the county and much of what is now England was a shallow tropical sea. We call this period the Cretaceous ( Creta means chalk and also give its name to the island of Crete) and it was a time of runaway greenhouse gases, no ice at either pole, and seas as warm as hot baths. This runaway greenhouse world, with massive amounts of CO2 in the atmosphere, was eventually brought back into balance by the billions of tonnes of atmospheric carbon locked away by coccolithophores. Their skeletal plates form Norfolk, England’s and the world’s chalk deposits. Coccolithophores make their coccoliths (skeletal plates) out of one part carbon, one part calcium and three parts oxygen (CaCO3). So each time a molecule of coccolith is made, one less carbon atom is allowed to roam freely in the world to form greenhouse gases and contribute to global warming.

We don’t perhaps appreciate the influence of this chalk in Norfolk. We only really notice it in the cliffs at Hunstanton where white chalk overlies the iron rich red chalk. I don’t know how tall those cliffs are but I do know each cm took about 1,000 years of deposition of the calcite skeletons of the coccolithospheres to create. Without the chalk there would be no flint nodules ( the remains of silica rich marine species and subject of a future post) and without the flint no hand axes from Grimes Graves and perhaps no homo sapiens. For surely we as a species would be very different if we hadn’t had millennia of flint tool usage to hone our hunting skills during our Stone Age evolution.

No coccolithosphores, no chalk deposits, no Norfolk and perhaps no modern human beings.

Simple really! So perhaps Emilania huxleyi, and its marine relatives, deserve to be appreciated and celebrated. They continue of course, unthanked, unrecognised and largely unknown to this day to regulate our climate by mopping up humanities carbon dioxide pollution from the air, continuing to lock it away in ‘carbon sinks’ on the world’s sea floors in deposits of grey ooze that Thomas Huxley first investigated. They are one of the planets keystone species, the base of ocean foodchains with zooplankton and small fish feeding directly on them. They produce dimethyl sulphide which released into the atmosphere from the ocean surface is thought to have a global impact on rainfall through ‘cloud seeding’. Their tiny bodies are rich in long chain poly-unsaturated lipids and are now being investigated as a possible future source of bio-fuels.

It took a great mind like Thomas Huxley’s to begin to see what an important part this species has played in the history of the world. The name Emaliania huxleyi of course recognises his discoveries. I hope if you have got this far that you too will recognise they deserve their place in the 100 species that made Norfolk.

1 comment:

  1. I think you have the makings of a new NWT book in your '100 Norfolk species', David.