Giant algal bloom explains the White Cliffs of Dover

The White Cliffs of Dover were formed 100 million years ago by chalk derived from the shells of ancient microorganisms. Photo by Platslee/Shutterstock

DOVER, England, Sept. 20 (UPI) — A massive algae bloom in the Southern Ocean is helping scientists understand how the White Cliffs of Dover came to be some 100 million years ago.

The iconic white cliffs that stretch more than 10 miles along the southern coast of England are composed of chalk, and the chalk is derived from calcite shells of tiny microorganisms called coccolithophores.

The single-cell algae armor themselves with saucer-like calcite plates. When they die, their calcite casings accumulate on the ocean floor. Over time, they’re compacted into chalk.

In the Southern Ocean, the phenomenon is happening on a massive scale. Researchers say the Great Calcite Belt reveals the oceanic conditions that made the White Cliffs of Dover possible, and offers new insights into the global carbon cycle.

“The Great Calcite Belt is significant because this gigantic area of the ocean is full of these organisms that are fixing carbon,” William Balch, a biological oceanographer at Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine, explained in a news release.

Every year, during the Southern Hemisphere’s summer months, the ocean water surrounding Antarctica shimmers a bright turquoise blue. Millions of coccolithophores act like tiny mirrors, reflecting the sunlight and brightening the ocean water.

Balch and his research partners were the first to credit coccolithophores with the phenomenon now known as the Great Calcite Belt.

Their survey revealed heightened concentrations of nitrate, silicate and iron — preferred nutrients of coccolithophores. Their analysis showed coccolithophores trap carbon more efficiently than their main algal competition, large diatoms, but the formation of their calcite plates also released CO2 into the surrounding ocean water.

As for their geological impact, researchers say it isn’t clear if more chalk cliffs are in the works. The White Cliffs of Dover were formed over millions of years.

“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 research into the Great Calcite Belt was recently detailed in two new studies, published in the journals Global Biogeochemical Cycles and Geology.


Please enter your comment!
Please enter your name here