These things did - coccolithophores, by the bucket load.
Coccolithophores are very small to minute spheroidal, biflagellate, unicellular marine phytoplankton with yellow-brown chloroplasts and characterised by an exoskeleton comprising intricate calcite (calcium carbonate, CaCO3) scales called coccoliths. However, what they lack in size they more than make up for in design beauty. They may also be present in such massive numbers that present-day blooms of the algae, covering vast areas of the sea, are easily visible to low Earth orbit (438miles, 708km) satellites and even make news headlines.
A massive bloom of coccolithophore Emiliania huxleyi in the Barents Sea
off the coast of Norway, August 2011.
The variations in bloom brightness and colour is partly due to its depth.
Emiliania huxleyi can grow luxuriantly to a depth of 50 metres. NASA image courtesy of Jeff Schmaltz
These modern-day algae have an ancestry dating back millions of years to the Cretaceous period when they too were present in vast numbers throughout that time. As they lived and died their remains fell as marine 'snow' at sedimentation rates often exceeding 10cm per thousand years(1) settling to form a thick mud. Over millions of years these sediments built-up forming deposits tens of metres (hundreds of feet) thick that subsequently became compacted and hardened into a soft, friable rock. This material in turn was uplifted by plate tectonics and together with changes in sea level became exposed then eroded to form the chalk cliffs and landscape synonymous of central-southern and south-east England.
Looking good for ~85.5 million years old.
Scanning electron micrographs of fossil coccolithophores, possibly Coccolithus sp. or Watznaueria sp.
isolated from chalk samples collected at Birling Gap, East Sussex, UK. Though millions upon millions of the organisms lived and died over tens of millions of years, in relative terms, very few intact specimens have survived through to modernity. However, with such huge numbers involved even the survival of a small fraction of a percent means many millions still made it through to present day in one piece. They are extremely abundant despite their miniscule size and perceived fragility which is just that - perceived.
Further examples of intact coccolithophores. Left and centre images: scanning electron micrographs.
Right image: high magnification photomicrograph (Oil immersion x100, N.A. 1.35) of isolated coccolithophore.
|Two relatively low magnification electron micrographs clearly showing the fossil remains of foraminifera embedded in (left image) and protruding from (right image) the matrix of coccoliths and individual calcite crystals that were once part of coccolithophore exoskeletons. The chalk samples were fractured to expose a fresh surface then freed from loose material with a jet of compressed air.
Scanning electron micrographs of detached coccoliths and calcite crystals that once formed structural components of coccoliths.
Sample prepared as above.
Surviving intact, coccolithophores poking out from the remains of the relatives that didn't.
It has been reported(2) that population densities of contemporary coccolithophores can reach in excess of 100,000 cells per litre but data vary widely, this figure being somewhere in the middle. Apparently (original source remains elusive) scientists also suggest that coccolithophores are the leading producers of marine calcite estimating that more than 1.4 billion kilogrammes are deposited by them each year as a result of their activity.(3) Towards the end of the 1990s, detached (free-floating) coccoliths reached concentrations of nearly 6 million per millilitre during Summer blooms of the algae in the Bering Sea.(4)
Even if population density and marine biomass alone are taken into consideration, these algae must have played an important role in the past in both carbon and calcium turnover. With climate change (anthropogenic or otherwise) and ocean neutralisation (real of not) the hot topics of the moment, these algae are going to come under ever-increasing scrutiny. They are obviously survivors, they weathered the Cretaceous–Paleogene (K–Pg) extinction event a few years ago and no doubt will see us out, humans, their distant relatives(5) that is.
Calcite crystals and fossil coccoliths frequently contaminate the tests of fossil foraminifera both within the walls and on the surface. This probably suggests that their incorporation into tests is more than simple contamination but that recycling or reuse has taken place.
A mind boggling thought to ponder.
Out of curiosity, I attempted one of those pointless calculations to reckon how many intact coccolithophores might be contained within a cubic centimetre. The average diametre of the coccolithophores found to date is about 10µm. Applying the formula (v=4/3.Pi.r3) for the volume of a sphere, we get 524µm3. Since there are 1x1012 cubic microns (i.e. 1,000,000,000,000) in 1cm3, by calculation we get 1.9 billion coccoliths per cubic centimetre. For those who prefer imperial units, 1 cubic inch is equivalent to 1.64x1013 (i.e. 16,400,000,000,000) cubic microns which, dividing by 524, equates to 3.1x1010 (31,000,000,000) coccoliths per cubic inch.
Current guesstimates by the United Nations for human world population stands at around 7.4 billion. This implies there are more than 4 times the number of coccolithophores in a cubic inch of chalk than there are humans currently living on the planet. With deposits hundreds of feet thick and covering an area of hundreds of square miles, consider the volume of chalk in Southern England alone and imagine the number of coccoliths that created the deposits.
1. Sedimentary Basins: Evolution, Facies, and Sediment Budget. Chapter 5, p.192. G. Einsele. Springer-Verlag Berlin Heidelberg New York
2. Coccolithophore dynamics off Bermuda (N.Atlentic). Ali T. Haidar, Hans R. Thierstein. Deep-Sea Research II 48 (2001) 1925-1956
3. What is a Coccolithophore? John Weier. NASA Earth Observatory, 26 April, 1999.
4. Changing Currents Colour the Bering Sea a New Shade of Blue. John Weier. NASA Earth Observatory, 30 March, 1999.
5. Will Ion Channels Help Coccolithophores Adapt to Ocean Acidification? Mejia R (2011). PLoS Biol 9(6): e1001087.