ROCKPORT — For the past several days, seaweed has been moving in on the tide through Rockport’s outer and inner harbor. With barely any stirring breezes, it has quietly been rafting into a carpet of brown.

Weather has been hot, even on the shore. Logs, white styrofoam coffee cups and plastic bottles are getting caught up in those seaweed rafts, and the response looking out over harbor has generally been, “that’s just gross,” or, “you can walk to your boat.”

On the other hand, this seaweed is loaded with minerals that are beneficial to gardens and farms. With a boat, rake and truck, it could be a bonanza for an entrepreneur.

Rafts of seaweed are not uncommon, according to Sarah Redmond, a marine extension associate at the Maine Sea Grant Program. Rockport Harbor just happens to be a receptacle this summer.

The seaweed is more officially known as rockweed, and is the most common ocean plant along Maine’s coast. It has the bubbles — or bladder wrack, or knotted wrack — which keep it floating. It is a perennial and summer is the height of its growth cycle. There are a variety of reasons why is collecting this week in Rockport.

“Its a pretty natural process,” said Redmond, who works in Franklin at the Maine Center for Cooperative Aquaculture Research. “The state of Maine is full of rockweed. Every intertidal area has it.”

The plants, she said, are branchy, and can be weakened by snails or other grazers. The rockweed loses up to 50 percent of mass every year through its growth cycle.

Plus, the rockweed grows in environments with energetic variables. Tides are constant, but they vary in height according to the moon and the pull of the ocean.

Then, there are currents, rain, storm surges and wind, all of which add more dynamics.

The prevailing wind in the summer along Maine’s coast is out of the southwest. Rockport Harbor, though long and deep, is open to those prevailing winds. Offshore storms can kick up swells that move into Penobscot Bay, and eventually into harbors. The extreme tides in July and the two full moons all create contributing forces.

Trying to pin down the exact variables that caused the rockweed to collect in Rockport Harbor — while leaving other harbors alone — would be an inexact exercise.

“It just happens to be,” said Redmond.

The rockweed collects and drifts together in masses, kind of like how, “Cheerios and milk stick together,” said Redmond.

“People notice in their front yard, or harbor, or beach, but it is completely natural,” she said. “With all of these reports of unattached seaweeds, it is certainly one thing to think about for farmers and gardeners.”

The minerals it absorbs from the ocean give it value for gardens, as it breaks down into useful compost.  The rockweed picks up the minerals from land that have washed into the ocean.

The growth in the business of harvesting seawood for commercial ventures has compelled the Maine Department of Marine Resources to establish a Rockweed Working Group to implement a Rockweed Fishery Management Plan. The group’s purpose is to determine the effect of commercial rockweed harvest on wildlife, and recommend areas to close to commercial harvest (DMR Fishery Management Plan for Rockweed).

The rockweed is full of useful nutrients, and is considered a sign of good water quality. It declines in abundance with pollution. Rockweed is also integral to habitat for many creatures, such crabs, baby mussels, snails, periwinkles, young pollack, all which attract sea and shore birds.

In the case of Rockport Harbor, this week, “There's an opportunity if the right person wants to scoop it up in a net,” said Redmond, recounting how a farmer in Virginia once called her inquiring about the possibility of getting a truckload of seaweed delivered down there.

“It’s a matter of connecting all the dots,” she said. “Harbors and beaches could call somebody to come scoop up this floating mass, and provide a service.”

On Aug. 29, the annual Maine Seaweed Festival takes place on the campus of Southern Maine Community College, in South Portland. Its purpose is “raise awareness and educate the public about the impacts Maine Macroalgae is having in our local food culture, agriculture and aquaculture industries, as well as the academic arts and sciences. We also strive to highlight local value-added products and services that utilize Maine Seaweeds. Sea you there!”

Reach Editorial Director Lynda Clancy at lyndaclancy@penbaypilot.com; 207-706-6657