Kelp Strengthening Maine's Marine Economy

Maine's coastal waters are becoming more acidic due to climate change, but the aquaculture industry may have a profitable, delicious source of help close at hand: kelp. Bigelow Laboratory Senior Research Scientist Nichole Price is working with local shellfish farmers to capitalize on the unique ocean remediation opportunity offered by growing seaweed on their farms.

“Of all the potential ways to address climate change, I'm pursuing phytoremediation because it can be done on existing infrastructure and generates a new revenue stream,” said Price, who also directs Bigelow Laboratory’s Center for Venture Research. “It also creates a nutritious, edible product in a world of increasing food insecurity.”

Since the Industrial Revolution, human activities have pumped an excess of carbon dioxide into the atmosphere. Some of this carbon dissolves into the ocean, making its pH more acidic, and the water less habitable for many ocean plants and animals.

Kelp, however, soaks up carbon like a sponge as it grows. By removing CO₂ from the surrounding seawater, it makes that water less acidic. This can create a "halo" of remediated water around seaweed farms, improving growth conditions for shellfish in the area.

Acidic seawater weakens and degrades the shells that protect animals like mussels, oysters, and clams, and makes them less healthy. For shellfish farmers, ocean acidification is a major threat to their stocks — especially larval and juvenile shellfish, who are the most vulnerable to acidic conditions.

“On both the East and West Coast, the shellfish industry is extremely aware of the threats posed by ocean acidification,” Price said. “We’ve got to do something now and put the power in the hands of shellfishermen.”

Seaweed and shellfish just may be the answer, and a match made in heaven. Growing kelp can naturally buffer seawater acidity on shellfish farms – and create another revenue stream for farmers in the process. Uses for kelp range from culinary to agricultural. In addition to soaking up excess carbon in the ocean, feeding kelp to cows decreases their production of methane, another powerful greenhouse gas.

Price is part of a growing kelp aquaculture movement in the United States, and believes this new crop can help both farmers and their local environments, in coastal Maine and beyond. In fact, the potential of the nascent kelp aquaculture industry drew her to Maine four years ago. Today, she has worked alongside a number of local partners to do novel research on the halo effect and the potential of kelp to aid ocean remediation.

“Everything that we've done has been hand-in-hand with farmers,” Price said. “The measurements we make and the theories we test are really pragmatic from a farmer’s perspective, so what we learn can be directly applied.”

Many of these measurements have aimed to explore the potential benefits of the halo effect by quantifying it in time and space. With the Island Institute in Rockland, Price moored oceanographic instruments both inside and outside a kelp farm to track how the water quality changed over time. Her team also partnered with scientists from University of New Hampshire to drive a small boat around the Ocean Approved kelp farm in Casco Bay, recording the amount of carbon dioxide in the water. These measurements allowed her to create a series of “heat maps” that illustrate how far the halo extends from the farm, and how factors like tides, rain, and sunshine contribute to its size and consistency.

“We’ve seen that growing cultured seaweed creates a bubble of better water emanating from the farm, and it changes throughout the year,” Price said. “That could be important in Maine's bays and estuaries that are targeted for aquaculture or conservation of certain shellfish species.”

This summer, Price ran an experiment to learn how growing mussels alongside kelp affects the shellfish. She installed juveniles from Bangs Island Mussels farm in cages both inside and outside the Ocean Approved kelp farm. Once the mussels had grown for several months, Price’s summer intern tested how much pressure the shells could withstand before breaking. The tests simulated the bumping and jostling mussels often experience on their way from the sea to a dinner plate, which can crush their shells and make them inedible. The initial results look promising: mussels grown inside the kelp’s halo of better water quality seem more resilient than those grown outside the farm.

This finding is the first evidence that mussels benefit from being grown next to kelp. In addition, Price’s time series experiment showed that the halo effect can actually make Maine’s waters hospitable to shellfish farming earlier in the spring. This means a heartier crop, a longer growing season, and a shorter time until shellfish reach market size — all positive effects that Price hopes will encourage more shellfish farmers to try raising kelp.

“The first seaweed farm in the United States was here in Maine, where sugar kelp is a native ecosystem engineer,” Price said. “There is so much potential for a profitable, sustainable industry. If Mainers are interested, there's a lot of room for expansion here.”

The middle image shows Susie Arnold, a marine scientist at the Island Institute, preparing mussels for deployment in an experiment at the Ocean Approved kelp farm in Casco Bay. All photos courtesy of Brittney Honisch.