For 15 years, shore-front property owners, rockweed cutters and Maine Department of Marine Resources regulators have attempted to balance the competing interests that have tended to define the state’s rockweed industry.

Maine case law has produced mixed opinions on the question of who actually owns the olive-brown algae that is used in fertilizer and in some consumable products.

But a Washington County Superior Court case could help settle what’s become a contentious rockweed debate.

At high tide, rockweed floats on the water’s surface along the Maine coast, its rubbery, olive-brown plant strands buoyed by a series of air bladders. At low tide, it drapes shore-front rocks to provide protective habitat for crabs and other creatures. It was a source of fertilizer for English colonists who spelled out access rights in the Massachusetts Bay Colony’s Colonial Ordinance of 1641-1647. Since then, though, who owns Maine’s rockweed – or Ascophyllum nodosum, as it is known in scientific circles – remains an unanswered question for property owners, conservationists and harvesters.

Gordon Smith is a Portland attorney who represents several Washington County landowners upset that their shore-front properties have become targets for rockweed harvesters. They’ve made Acadian Seaplants Ltd. the focus of a lawsuit filed in Superior Court. The Nova Scotian biotech company is the largest independent manufacturer of marine plant products of its type in the world. Smith says that based on his reading of case law, it is clear to him that landowners control access in the intertidal zone of their property – a point he repeatedly made during arguments in court last week.

“Even in Massachusetts, there has not been a clear statement about whether or not the harvest of rockweed, or inter-tidal seaweed in general, there hasn’t been a definitive statement on whether that falls within the scope of the public trust doctrine,” Smith said. “At the Superior Court level where we are right now I think the judge is going to be much more inclined to look at the legal principles the parties have raised that may be old, but are still relevant.”

Smith is basing part of his argument on a Civil War-era Maine case in which the court concluded that, “title to the seaweed is in the owner of the flats” and that “seaweed belongs to the owner of the soil upon which it grows or is deposited.” Exceptions granted by the court at that time include access by those engaged in fishing, fowling and navigation. Modern Maine law maintains that the state, “owns and shall control the harvesting of the living resources of the seas adjoining the coastline.”

JP Deveau, president of Acadian Seaplants, says he interprets that to mean that rockweed – just like clams, marine worms and periwinkles – is a harvestable organism in Maine.

“So if we make the assumption that if the court decides that this is a public resource, then what we would like to see the state do and I think the state is very open to this, is that they would then come with a proper, licensing program that would make sure that the resource and the harvesting of the resource would be managed properly in a long-term sustainable way,” Deveau said.

At the Maine Department of Marine Resources, spokesman Jeff Nichols says while Maine statutes authorize the DMR commissioner to regulate the harvest of seaweed, the question of who owns the plant remains unresolved. According to the DMR, in 2014, Maine’s seaweed harvest amounted to more than 17 million pounds. More than 90 percent of the estimated $20 million annual Maine seaweed harvest is of the rockweed variety and Deveau says he favors any interpretation by the courts that continues to provide his company with access to Maine rockweed – including a provision for exclusion zones.

“In Canada, in some of the licenses that we have, the government has indicated that we want these as either study areas or exclusion zones for various reasons,” said Deveau, “And certainly we’ve worked with the government to cooperatively to find the path and say that we understand that you would not want to see seaweed harvesting in this specific area and that’s fine and then it would be OK in other areas.”

How rockweed sustainability is defined is a major issue for Robin Hadlock Seeley, senior researcher at the Shoals Marine Lab at Cornell University. What Deveau and others need to assess, she says, is the impact that harvesting has on the dozens and dozens of marine animals that require the protection of the rockweed beds just to survive to maturity.

“So the industry is looking at sustainability and asking the question: How much can we cut and how quickly does it come back so that we can cut it again?” Seeley said, “and so from an ecological point of view, because this is habitat, we can’t simply treat as as a biomass, we have to treat it as habitat and we have to say: How much can you cut and still have it retain the same ecosystem function that it started with?”

A decision could come later this month. No matter how it unfolds, it’s expected that it will be appealed to the Maine Supreme Court.

This article appears through a media partnership with Maine Public.