Scientists have figured out how to measure the red glow emitted by marine phytoplankton, giving them an important new tool for assessing the ocean's health.

Weekly planet-wide satellite measurements of the organisms' fluorescence will be critical in evaluating the effect on marine life of global warming, climate change, desertification and other changes, the researchers say.

"Until now we've really struggled to make this technology work and give us the information we need," Oregon State University botanist Michael Behrenfeld said in a release.

"The fluorescence measurements allow us to see from outer space the faint red glow of tiny marine plants, all over the world, and tell whether or not they are healthy. That's pretty cool."

Behrenfeld and colleagues at NASA and other organizations said Thursday the information they expect to collect will help assess which areas of the ocean are limited in their productivity.

Phytoplankton are single-celled organisms and are the base of the marine food chain. As such, their health is intrinsically tied to the broader health and productivity of the ocean.

Phytoplankton absorb energy from the sun, and then release some of that energy as dim red glow called fluorescence. Measuring that glow gives researchers a good idea of the number of phytoplankton.

Up till now, scientists had to rely on measurements of phytoplankton biomass or their carbon-to-chlorophyll ratio to get a handle on their numbers.

While such tools are helpful, they give only part of the picture because measurements can only be taken for tiny portions of the ocean at a time.