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February 4, 2021

Bigelow researchers explore seaweed farming's benefits for ocean health

Courtesy / Island Institute Bigelow Laboratory Research Associate Brittney Honisch measures a piece of sugar kelp before harvest in Casco Bay. Bigelow Laboratory is leading a new project to evaluate how seaweed might mitigate coastal acidification.

A new study in Maine will look at the ability of a type of seaweed called kelp to make the ocean more habitable for marine organisms, and possibly increase what's harvested from it. 

East Boothbay’s Bigelow Laboratory for Ocean Sciences has received a $900,000 grant to study how kelp aquaculture can counteract effects of climate change. The international project was funded by World Wildlife Fund with support from the Bezos Earth Fund.

The goal of the project is to inform farmers, the public and policymakers, and ultimately to help restore the health and productivity of the oceans.

With partners from the Island Institute and the University of New Hampshire, Senior Research Scientist Nichole Price, the project lead, has been working with mussel and seaweed farmers in Maine to test the potential of growing kelp alongside blue mussels, which are particularly vulnerable to increasing ocean acidity.

In protected bays, growing kelp can naturally buffer seawater acidity and create an additional product for harvest in the process.

"Not only does this give us two commercially viable crops, but it also allows us to increase the positive impact on our local ecosystem," said Matthew Moretti, CEO of Bangs Island Mussels, a Maine farm that has been collaborating with the researchers. "In the face of a rapidly changing environment, this is even more important."

Global seaweed harvest is already projected to reach more than $30 billion by 2025. Cultivated seaweed grows quickly and requires minimal resources, such as land or freshwater, providing a sustainable food source and making it an attractive crop for rural coastal communities facing dwindling wild-capture fisheries.

Acidic water

Carbon dioxide is accumulating in the atmosphere at alarming concentrations due to human activity, and some of this greenhouse gas dissolves into the ocean's surface waters. The result is that the water is becoming more acidic and less habitable for many species.

Kelp, however, soaks up carbon dioxide like a sponge. The process can lower the acidity of the surrounding seawater and raise oxygen levels, creating a temporary "halo" area of improved water conditions that can benefit other sea life in the area.

Traditionally, research on how marine photosynthetic organisms mitigate climate change and sequester carbon — referred to as "blue carbon" — has focused on seagrasses, salt marshes and mangroves.

"The role of kelp aquaculture has been relatively unexplored, despite its great potential to reduce carbon dioxide concentration and seawater acidity with benefits for the shellfish industry and surrounding coastal areas," said Aurora Martinez Ricart, a Bigelow Laboratory postdoctoral researcher and co-investigator on the project.

The past year has been the warmest on record, noted Price.

Profit and ecology

The grant will allow the researchers to expand their partnerships and research into kelp's positive environmental impacts and potential applications. The scientists will collaborate with others to monitor water quality during and after the growing season at three kelp farms in Maine, Alaska and Norway. The team will track carbon dioxide, oxygen, and nutrient concentrations, as well as basic metrics such as salinity and temperature.

The researchers will use the information to create a computer model of water circulation, kelp growth and resulting water quality changes that is expected to enable them to better understand farmed kelp's impact at the study farms, and predict kelp's effects in other locations.

"Seaweed farming has the possibility to provide not only diversification and profit for struggling working waterfronts, but also critical ecosystem services for coastal marine systems," said Price. "However, to earn the social acceptance of aquaculture, we need to rigorously document evidence of these water quality benefits across a range of settings."

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