A portion of the White Cliffs of Dover. Image: Janis Smits/Shutterstock
How a particular type of algae dominated over another has been found to answer why the White Cliffs of Dover are so white, but could it also show that a new set of cliffs are developing off the coast of Antarctica?
Since Roman times, the brilliant White Cliffs of Dover have been the first thing travellers across the English Channel likely saw of Britain.
Standing 110m high and stretching over 16km of coastline, the chalk cliffs were formed by minute single-celled algae called coccolithophores that build hardened calcite shells around themselves.
When these algae died, they built up over time to form thick layers of chalk approximately 100m years ago where they lay on a shallow sea floor before gradually being pushed up by the Earth’s crust.
However, this formation could not be properly analysed as no similar examples on such a scale have been examined by science – until now.
Found in the Southern Ocean that surrounds Antarctica, the Great Calcite Belt that consists of a huge algal bloom of coccolithophores has now been analysed by researchers from the Bigelow Laboratory for Ocean Sciences in the US.
A microscopic view of a coccolithophore shows the saucer-shaped calcite plates the algae build around themselves. Image: Alison R. Taylor/University of North Carolina Wilmington Microscopy Facility via Wikimedia Commons (CC BY 2.5)
Three key nutrients at play
By looking at this enormous bloom, the researchers hoped to determine what exactly leads to high formation rates of this particular algae and why they tend to out-perform other algae.
It turns out that high populations of coccolithophores are found in areas that have three key nutrients: nitrate, silicate and iron.
The quantity of each of these minerals plays a part in a fine balance as to whether one type of algae dominates over another.
In areas where there is an abundance of silicate, the algae diatom will dominate, but areas where nitrate is abundant see coccolithophores dominate.
Yet, the deciding factor in why the latter dominates the Southern Ocean was found to be that coccolithophores grow better in iron, whereas diatoms do not.
A coccolithophore bloom in the Barents Sea. Image: Jeff Schmaltz/NASA Earth Observatory
New Cliffs of Dover?
So could a new White Cliffs of Dover be forming in the Antarctic?
Speaking with the American Geophysical Union, oceanographer Marlon Lewis – not involved with the study – said it is difficult to tell whether this bloom will one day contribute to a giant geological structure.
In order to achieve it, he said, many layers of calcite would be needed over millions of years and there is no guarantee this will happen.
However, the study’s lead author, William Balch, appears to be optimistic of its chances.
“While we don’t have the great cliffs of the Southern Ocean, there is solid evidence that the calcite is making it to the sea floor,” he said.
The team’s study has been published in the journal Global Biogeochemical Cycles.
