Article in the Mount Desert Islander
Local scientists raise concerns about commercial rockweed harvesting
- By Rebecca Alley
- Dec 2, 2025
BLUE HILL PENINSULA — Local scientists are raising concerns about the lack of research regarding the long-term impacts of commercial rockweed harvesting.
Dr. David Porter, a retired professor from the University of Georgia, and Dr. Allison Snow, a retired professor from the University of Massachusetts at Amherst, have published a scientific review article in the Journal of Marine Science and Engineering, concluding that more rigorous research should be completed to help better understand how to protect the marine resource.
“Rockweed is a slow-growing, perennial seaweed that flourishes on rocky shores of the Gulf of Maine,” explained Porter. “Ecologically, rockweed is considered a foundation species because it supports scores of invertebrate species, fish, shore birds, and other wildlife, forming an underwater forest at high tide and a moisturizing blanket over rocks and nearby mudflats at low tide.”
It’s also commercially harvested in Canada, with Porter and Snow noting that additional experimental study is needed in Nova Scotia as well.
Rockweed is a marine resource that has captured Porter’s interest since he was a child, as he spent every summer with his family on the Maine coast in Penobscot.
“When I was a kid in the summertime, I would always be interested in walking along the beach and seeing what’s there. My scientific interest was probably initiated as a child,” he said.
After retiring and moving to Maine in 2009, Porter formed the Blue Hill Peninsula Rockweed Forum with Snow.
The mission of the volunteer organization “is to advocate for the conservation of intertidal rockweed (Ascophyllum nodosum) and its service to the marine ecosystem,” according to the forum’s website.
“We both got concerned about it and decided to establish the local rockweed forum to help educate people and shoreland owners of the potential threat to this ecosystem,” Porter said.
The potential threats largely have to do with large-scale, commercial harvesting efforts by large companies, Porter explained.
That, coupled with the limited scientific studies on the long-term impacts of harvesting, raise concerns for the health of the resource that is integral to the intertidal ecosystem.
“The commercial harvesters, and even some of the scientists, say the rockweed biomass … is replaced after harvesting … within three years,” Porter said. “But what our group is really concerned about is the ecosystem function.”
To explain that further, Porter compared a harvested rockweed plant to a tree that has been cut down to a shrub.
While the shrub may still be alive and may still be functioning, it’s functioning in a different way and creates a completely different ecosystem than its original tree.
Porter noted that smaller-scale harvesting endeavors do not pose the same kind of risk.
“I think that small-scale harvesting, even for small-scale commercial harvesting, can be beneficial as well,” he said.
There is a balance to be struck, as imposing an outright ban on harvesting rockweed is “an unreasonable point of view,” Porter said. “It’s a valuable resource that has been shown to be useful from an agricultural standpoint.”
“Rockweed also has great commercial value that supports industrial-scale harvesting. Each year, thousands of tons of rockweed are extracted from the Gulf of Maine and processed as soil conditioners, fertilizers, crop biostimulants and other products,” Porter said. “Rockweed is rarely killed by harvesting because the fronds are cut off above a sturdy basal holdfast that can sprout new shoots. A major research question, then, is how quickly can rockweed grow back and recover its natural biomass and 3-6 foot height after different intensities of harvesting?”
That is where more comprehensive studies and more regulations are needed, Porter explained. That includes research conducted by independent scientists who don’t have vested interests in the commercial value of rockweed, he added.
Current regulations require harvesters to ensure that they leave a minimum of 16 inches of the rockweed above the holdfast to help with regeneration.
Harvesters, since they are working in the intertidal zone, must also be granted permission by landowners, Porter explained.
But that regulation can cause friction between landowners and harvesters, said Porter, who suggested that there be specific research areas that remain untouched to help establish a baseline to understand the nature of the rockweed forest.
He also suggested establishing areas where harvesting can occur in a more controlled way.