Selecting a Seaweed Species

Introduction

The cold, clean waters of the Gulf of Maine are an ideal habitat for the diverse array of over 250 cold-water seaweed species native to the region. Average temperatures in the Gulf of Maine over the past decade fluctuated between ~51 degrees F to ~54 degrees F, which falls within the range of many cold-water seaweed species. Nutrients such as nitrogen and phosphorus that are critical to the growth of seaweeds are in ample supply in the Gulf of Maine and are generally provided by two deep-water ocean currents. Nutrient levels in coastal waters are also impacted by terrestrial runoff, which can result in additional nutrients available to organisms growing in near-shore waters. Finally, the Maine coast is full of shallow, subtidal environments with rocky substrates that receive adequate sunlight for photosynthesis– the perfect conditions for growing seaweed. With roughly 3,500 miles of coastline opening into the cold, nutrient-rich waters of the Gulf of Maine, Maine has more prime space for growing seaweeds than almost any other US state!

What to farm?

Among the first considerations for selecting a seaweed species to farm in Maine are:

  1. ecological factors in your area
  2. the natural availability of a given seaweed in your local environment (a.k.a. Is it a native species or species that occurs in Maine), and
  3. the practical financial questions: how much money can I make by selling macroalga X and who am I going to sell it to

Every species of seaweed is adapted to specific habitat characteristics depending on how much light it needs, its tolerance to wave action and currents, the substrateA substance or surface that an organism grows and lives on or is supported by. it grows on, and what nutrients are available. Therefore, picking a seaweed appropriate to your environment is key. It is also important to note that only seaweeds that are native to or occur in Maine are allowed to be farmed in the state’s coastal waters. Of the 250 seaweed species found in Maine, approximately 10 are currently harvested or farmed commercially:

Rockweed

-Ascophyllum nodosum

-Brown algae

-Wild harvest

-Used in fertilizer, animal feed

Image credit: Maine Seaweed Council

Skinny Kelp

-Sachharina angustissima, variety of sugar kelp

-Brown algae

-Farmed

-Used for human food

Image credit: Maine Seaweed Council

Sugar Kelp

-Saccharina latissima

-Brown algae

-Farmed, wild harvest

-Used for human food

Image credit: Maine Seaweed Council

Nori

-Porphyra spp.

-Red algae

-Wild harvest

-Used in human food

Image credit: Maine Seaweed Council

Irish Moss

-Ulva lactuca

-Green algae

-Wild harvest

-Used in human food

Image credit: Maine Seaweed Council

Horse Tail Kelp

-Laminaria digitata

-Brown algae

-Wild harvest, experimentally farmed

-Used for human food

Image credit: Maine Seaweed Council

Dulse

-Palmaria palmata

-Red algae

-Wild harvest, experimentally farmed

-Used in human food

Image credit: Maine Seaweed Council

Irish Moss

-Chondrus crispus

-Red algae

-Wild harvest

-Used in human food, carageenan

Image credit: Maine Seaweed Council

Winged Kelp

-Alaria esculenta

-Brown algae

-Farmed, wild harvest

-Used for human food

Image credit: Maine Seaweed Council

Bladder Wrack

-Fucus spp.

-Brown algae

-Wild harvest

-Used in fertilizer, animal feed

Image credit: Maine Seaweed Council

All of these species can be found naturally in Maine coastal waters, and all but skinny kelp are harvested in the wild for commercial markets.

Learn more about types of sea vegetables on the Maine Seaweed Council website and the Maine Coast Sea Vegetables website: 

What is the market?

Next, you’ll want to make sure that there is a market for the seaweed species you decide to grow and that you have a reliable buyer in mind for your seaweed crop. Seaweed markets in Maine and the U.S. are nascent or emerging, so identifying and securing an end market is particularly important for farms to be profitable. In Maine, the majority of farmed seaweed is sold by contract to value-added processors, though a smaller volume is processed by farmers, farmer cooperatives, or sold to restaurants or direct to consumer.

Seaweed is most often sold either by wet weight or by dry weight depending on preferences and processing capacity of producers and buyers/processors. Selling wet-weight product is often appealing to farmers because it doesn’t require any processing– like drying, blanching, or freezing– on their end. However, when buyers or processors are not located close to farms, selling wet-weight may be challenging to the very short shelf life of fresh, unprocessed seaweed. In those cases, farmers will have to consider the additional step of drying or stabilizing their seaweed to market it.

The market price per wet-pound of seaweed varies depending on a number of factors including (1) buyer, (2) the species of seaweed, (3) organic certification, and (4) farmed vs. wild origin. In Maine, the median market price that growers could expect to get per wet-pound of farmed kelp was $0.61 (based on a 2023 Maine Seaweed Benchmarking Report). Other seaweed species may have higher or lower value per wet-pound depending what they are being used for. Rockweed, for example, had a market value of around seven cents per wet pound as of 2023 based on data from the DMR. 

Despite higher market values for certain seaweed species, it is not necessarily possible for potential farmers to simply select the most valuable seaweed for their farm. As it turns out, cultivation strategies and technology are not yet available for most Maine seaweeds in this relatively young industry.

Specialized seaweed nursery technology

Seaweed nursery systems are a particularly prime example of a limiting technological factor for selecting a seaweed to farm in Maine. Because there is a lot of equipment, knowledge, and technical expertise that goes into raising juvenile seaweed, it is an expensive and time-consuming commitment to grow your own seed. If you plan to farm a seaweed species that does not have an existing seed-distributor in the state, you are committing to an involved process of research and nursery development in addition to crop grow-out on the farm.

Image credit: USDA Climate Hub

What does it mean that the ‘cultivation strategies and technology are not available’? Essentially, at present, we don’t have the biological understanding or cultivation technology to farm seaweeds other than sugar kelp (Saccharina latissima), winged kelp (Alaria esculenta), and skinny kelp (Saccharina angustissima) at a commercial level in Maine (Horsetail kelp (Laminaria digitata) is also farmed, but only by one or two farms in the state). What is more, while commercial cultivation strategies for species similar to those in the state may exist in other places (e.g. the United Kingdom, Japan, China, or South Korea), the technologies needed to farm these seaweeds are not necessarily present in Maine at this time. Without this equipment and a cultivation strategy, even experimenting with new species could be a costly and risky business decision– particularly for farmers just starting out.

For this reason, most people in Maine skip the first two considerations entirely and come straight to the conclusion of farming kelp– usually sugar kelp to start.

Research on new species for farming
Research through the University of Maine and in the northeast is underway to develop aquaculture strategies for additional Maine seaweed including dulse (Palmaria palmata), Atlantic nori (Porphyra spp., Wildemania spp.), horsetail kelp (Laminaria digitata), and gracilaria (Gracilaria tikvahiae). Farmers interested in experimenting with nurseries for new Maine seaweed species can also work with Maine Aquaculture Innovation Center’s business incubator program at the University of Maine Darling Marine Center or the University of Maine Center for Cooperative Aquaculture Research to get started.

Image credit: Maine Sea Grant