New research on the impact of kelp farming in reducing local carbon dioxide levels shows that sugar, bull and ribbon kelp grown in Alaska are the most effective.

All three varieties are highly effective at absorbing dissolved carbon dioxide from seawater through rapid photosynthesis. Seaweed aquaculture mitigates atmospheric carbon via a series of natural processes and innovative farming techniques. As kelp farms grow, they continuously extract dissolved carbon dioxide from the water, prompting the ocean to absorb more.

The University of Alaska Fairbanks study, with a focus on kelp farms, recently published in the journal Ocean Science, was the first to measure marine carbon dioxide removal (mCDR) in Alaska waters.

It turns out that environmental impacts of kelp farming are very nuanced and there are many factors affecting the ability of kelp to lower carbon dioxide levels.

To learn what best determines the ability of a kelp farm to reduce carbon dioxide levels, UAF graduate student Josianne Haag installed sensors inside and outside kelp farms in Windy Bay near Cordova and Kalsin Bay on Kodiak Island. The sites differed in their size, growing season and tide conditions and growing seasons.

The study demonstrates that a farm site can influence overall air-sea CO2 flux, whereby farming structures create artificial habitat and that kelp farms are not always a net sink for atmospheric carbon. Overall, researchers concluded,the Windy Bay farm slightly reduced nearby atmospheric mCDR levels while the Kalsin Bay farm boosted them.

According to Josianne Haag, who led the project as a doctoral student, measurements will continue at the farms for at least two more years, but the first season showed that a kelp farm's recipe for carbon intake and output is complex.

The study was part of the Mariculture Research and Restoration Consortium project (Mar ReCon), funded by the Exxon Valdez Oil Spill Trustee Council.