It's a game-changer for scientists who monitor the world's marine life, from sharks to kelp forests and every living thing between.

For some time now, researchers have been gathering seawater and pumping it through a series of filters to capture environmental DNA (eDNA) shed by marine plants and animals.

That eDNA is then sequenced to identify precisely which species are present in specific areas.

If an area's biodiversity starts to change it can indicate trends such as declining fish stocks, deteriorating reef health and even exotic invasions that may threaten biosecurity.

But the task of harvesting eDNA has always been time-consuming, requiring researchers to laboriously filter seawater at the point of collection, or ship it back to a lab for filtration.

It has also required specialist gear including water pumps and access to a power source at sea, which is no easy thing.

But CSIRO researchers have changed all that after figuring out a shortcut.

They've found that cellulose filter paper left to soak in the ocean successfully sucks up precious eDNA, and there's no need for the hard work of machine-assisted filtering.

The discovery means the whole process is faster, simpler and can be conducted on a much broader scale.

Anyone with the right lightweight filter paper, and a way to immerse and retrieve it, might now be able to play a role in monitoring marine biodiversity.

In theory, it could mean an entire new army of citizen scientists helping to build a more detailed picture of the world's marine biome, which covers 70 per cent of the planet.

It will also make it easier for governments and industry to keep tabs on what's really going on beneath the waves.

"It means we can measure the environment at the scale and speed we really need to. Anybody could do this in any place and you don't need equipment," says Dr Olly Berry, director of the Environomics Future Science Platform at the CSIRO.

It was CSIRO marine scientist Cindy Bessey who initially began thinking about passive ways to collect eDNA after spending many hours at sea in a small dinghy with a water filter strapped to her back.

"It would take me nearly 30 minutes to filter water through just three filter papers at one site. I knew I needed to find a more efficient way if I was going to survey 100 sites," she said.

A study on her passive immersion method shows it works, and eDNA was successfully harvested from tropical Ashmore Reef and temperate Daw Island, off the West Australian coast.

"It is no longer necessary to filter seawater to collect eDNA, saving time and opening up the technology for use in places where access to equipment or power is limited," Dr Bessey said.

The CSIRO is now developing a simple device for passive eDNA collection in marine and fresh waterways.

The results of the study have been published in the Atlas of Living Australia.

Australian Associated Press