Scientists trying to save Tasmania's endangered giant kelp forests are calling on the public to record sightings of the seaweed by smartphone.
The underwater forests, which once dominated the state's east coast, have dwindled by more than 95 per cent over decades due to ocean warming and pollution.
"Scattered individuals and patches of giant kelp still survive, but there are few records of their locations," University of Tasmania Professor Craig Johnson said.
Prof Johnson is co-heading the citizen-science project which is aiming to map remaining kelp and help researchers identify any populations that may have adapted to warmer waters.
Kelp sightings can be recorded on a free smart phone app, Kelp Tracker, and will then be verified by scientists.
An Institute of Marine and Antarctic Studies project is working to restore the giant seaweed in waters off Tasmania.
In November, scientists finished installing hardware into rock at three restoration sites so lab-grown kelp can be planted in the wild.
"We will also use the data from the app to locate areas that might be suitable for habitat restoration," project co-lead Dr Cayne Layton said.
Kelp acts as an important habitat for weedy seadragons, rock lobster and abalone.
It can be identified by large wide leaves with air bladders at its base, stringy central stalk or stalks and a floating canopy.