Sustainable Aquaculture: New expertise and education efforts developed for New Hampshire’s growing interest in seaweed

by Becky Zeiber, New Hampshire Sea Grant

From kelp beer to seaweed salads, the public’s appetite for sea vegetables seems to have grown exponentially over the past few years. Although enthusiasm for these nutrient-packed macroalgae has been around for generations in New England, new expertise and educational opportunities are being developed to keep up with the recent uptick in demand for growing, harvesting and eating seaweed in New Hampshire and beyond. 

Blue mussels and various seaweeds grow on the IMTA raft mooring lines.

Two staff members from N. H. Sea Grant/UNH Cooperative Extension are collaborating on these endeavors — Michael Chambers, marine aquaculture specialist, works on the propagation and husbandry of various seaweed species, while Gabby Bradt, fisheries specialist, hosts workshops to educate the public about the benefits of eating seaweed and how to forage and prepare sea vegetables for eating them at home.

Chambers is relatively new to the seaweed aquaculture scene — he started growing kelp a few years ago near the mouth of the Piscataqua River, but he has learned a tremendous amount in a short time period. “Seaweed is such a clean product to grow, and it’s very exciting to be part of these efforts” he said.

Although kelp will grow naturally once the spores settle onto rocks or other hard surfaces, Chambers gives the process a boost with spools of line seeded with kelp spores. The difference is dramatic, with one spore per inch occurring naturally while Chambers says a spool can easily fit 1,000 spores per inch. The line is then set out horizontally on mooring lines or vertically in the water column on structures like the multi-trophic aquaculture cage, where the kelp can grow up to eight feet or longer and harvested when needed. A team of students in the two-semester UNH Ocean Projects Course is working on developing an underwater frame to culture kelp three meters below surface. Biology and engineering students are working closely to design, construct and deploy a kelp frame this winter for a spring harvest.

UNH graduate student Megan Peavey puts the final touches on a tank that will help grow kelp spores for later attachment to lines on the multi-trophic aquaculture raft.

Another approach being tested involves collecting wild specimens of seaweed like Gracilaria and dulse, tumbling small fragments of them with aeration in tanks to encourage rapid growth, then stringing them on a line and grow them out to their full size on lines in the ocean. Previous N.H. Sea Grant Doyle Fellows Megan Peavey (UNH ’16) and Jake Levine (UNH ’17) worked to develop this system over the summer at the UNH Jackson Estuarine Lab at Adams Point.

There’s an increasing interest from people who want to start up their own seaweed farms, and Bradt and Chambers are assisting with the permitting process. Would-be kelp farmers will need more infrastructure to help sell their product, though. There’s no seaweed processing facility in N.H. at the moment, which leaves the cleaning and prep work for the chef or forager to handle. If the state’s seaweed industry continues its forward momentum, there may be a need to invest in processing to help businesses scale up and sell their products, Bradt said.

The bottom line, though, is the taste; Bradt recently handed out seaweed smoothies at UNH’s Ocean Discovery Day for attendees to try, and the samples were such a hit with the younger crowd that she ran out of ingredients. Chambers envisions a world in the not-too-distant future where kids come home from school and snack on kelp chips. “They’d slam ‘em,” he said confidently.