Citizen Science Study Maps Oceans' Plankton

A study is calling on the world's sailors to help map the oceans' phytoplankton, microscopic plants that form the bedrock of marine food chains.

Researchers have developed an app for people to submit readings from Secchi disks - a method used since 1865.

The team hopes the data will help them understand what is happening beneath the waves.

They have been "astonished" by the response so far but are hoping for more readings from the southern hemisphere.

"The reason the project came about was because, in 2010, some Canadian scientists wrote a paper that suggested that the phytoplankton in the world's oceans had declined by 40% since the 1950s," explained project leader Richard Kirby, a research fellow at Plymouth University's Marine Institute.

"If true, this is a dramatic decline. As phytoplankton starts the food chain, they dictate the productivity at every level above," he observed.

"Ultimately, phytoplankton determines the amount of fish in the sea and the number of polar bears on the ice."