A type of algae, called diatoms, have been key to the evolution of the diversity of whales, according to a new study.

The research by Felix Marx of the University of Otago in New Zealand and Dr Mark Uhen of George Mason University in the US is published today in the journal Science.

"The fossil record clearly shows that diatoms and whales rose and fell in diversity together," says Marx, whose research was part of a PhD project under the supervision of Associate Professor Ewan Sordyce.

Marx and Uhen looked at the diversity of dolphins and whales (cetaceans) in the fossil record dating back 30 million years.

They then compared this with records of climate change and estimates of various food sources in the ocean.

Marx and Uhen measured the abundance of two different types of algae: nanoplankton and diatoms, which are key "primary producers" of the ocean - converting sunlight into food.

They found diatoms were the key to cetation diversity: The greater the diversity of diatoms found in the fossil record [a proxy for diatom abundance] the greater the diversity in species of whales and dolphins, says Marx.

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