It is the first time the composition of the seafloor, covering 70 percent of the Earth’s surface, has been mapped in 40 years; the most recent map was hand drawn in the 1970s.

Published in the latest edition of Geology, the map will help scientists better understand how our oceans have responded, and will respond, to environmental change. It also reveals the deep ocean basins to be much more complex than previously thought.

“In order to understand environmental change in the oceans we need to better understand what is preserved in the geological record in the seabed,” says lead researcher Dr Adriana Dutkiewicz from the University of Sydney.

“The deep ocean floor is a graveyard with much of it made up of the remains of microscopic sea creatures called phytoplankton, which thrive in sunlit surface waters. The composition of these remains can help decipher how oceans have responded in the past to climate change.”

A special group of phytoplankton called diatoms produce about a quarter of the oxygen we breathe and make a bigger contribution to fighting global warming than most plants on land. Their dead remains sink to the bottom of the ocean, locking away their carbon.

The new seafloor geology map demonstrates that diatom accumulations on the seafloor are nearly entirely independent of diatom blooms in surface waters in the Southern Ocean.

“This disconnect demonstrates that we understand the carbon source, but not the sink,” says co-author Professor Dietmar Muller from the University of Sydney. More research is needed to better understand this relationship.