Stefan Claesson launches a drone to take pictures of rockweed along the Maine coast. Credit: Courtesy of Hannah Webber

A team of researchers is going to extraordinary heights to find out just how much of an ecologically and economically important seaweed grows along the Maine coast.

About 260 feet high, if you want to be exact.

Scientists from Maine Maritime Academy, Schoodic Institute and Bigelow Laboratory for Ocean Sciences have teamed up with a Maine-based drone specialist in an attempt to measure the amount of rockweed found in Maine’s waters. The team has been flying drones over several areas of the coast for the past three years to monitor the seaweed and create a map for harvesters and fishery managers.

This knowledge could be a potential boon to rockweed cutters who sell the seaweed for everything from animal feed to cosmetic products and environmentalists concerned about whether future harvests will continue to be sustainable.

Rockweed has grown into one of the largest wild-harvested seaweeds in Maine, ballooning from a $84,000 harvest in 2001 to just shy of $1 million 20 years later. The seaweed has become so valuable that a fight over who can harvest it in certain areas has been the subject of legal challenges all the way up to the state supreme court.

But even though the seaweed’s harvest has been argued over for years and it provides vital protection to a host of creatures in the intertidal area, no one has a firm grasp on just how much rockweed there is in Maine.

“Right now, we don’t know precisely where the resource is located and how much there is,” said Stefan Claesson, the principal scientist at Nearview — the company that’s been flying drones across the coast. “You really can’t do a good job managing the seaweed resource without that data.”

Claesson’s drones are equipped with spectral light sensors that can take thousands of pictures along the coast. Since 2019 he’s surveyed eight different areas, each between 25 and 50 acres, between Casco Bay and Cobscook Bay.

Those pictures are then analyzed to find a light signature that is specific to rockweed, and in turn paint a picture of how widespread the seaweed is on Maine’s rocky bottom.

“It’s not quite a fingerprint, but you can think of it that way,” Claesson said.

It’s an undertaking that would be nearly impossible without the drones and cameras.

In the past, this kind of work was done on the ground and researchers painstakingly looked at small plots for hours at low tide to study the seaweed. Drones can now do that same work in a fraction of the time and access remote places that scientists may have never reached before.

“There’d be no way a human being or a team of human beings could do that,” said Jessica Muhlin, a marine science professor at Maine Maritime Academy who has led the rockweed research.

The team will present some of their findings in a webinar next week and plan to continue fine tuning the algorithm that identifies the spectral light of the seaweed.

Claesson, who got a grant from the National Oceanic and Atmospheric Administration this year to build on his work, is also looking to test out the drones in a single area monthly to see if there are any changes to the spectral signature depending on the time of year.

The drone work has potential in other areas, too.

The method could be applied to find the light signature of other species. It also could measure how fragile ecosystems, such as Maine’s salt marshes and intertidal areas, are faring under increased pressure from rising levels of warmer and more acidic waters, said Hannah Webber, a scientist at the Schoodic Institute involved in the drone tests.

“Putting a drone up in the air allows us to be there more or less instantly to understand change,” she said.

Correction: An earlier version of this story misidentified what rockweed is. It is a seaweed.