Alaska kelp farms have varied effects on marine CO2 levels

Alaska kelp farms have varied effects on marine CO2 levels

Alaska kelp farms, which have been viewed as potential boon for reducing local carbon dioxide levels, have surprisingly murky effects on atmospheric CO₂ removal, according to a new study.

A University of Alaska Fairbanks-led project measured the amount of CO₂ that was emitted and absorbed at two kelp farms in the Gulf of Alaska during the 2023-2024 growing season. The outcome was mixed - one farm slightly reduced carbon dioxide in the local environment while the other added more to it.

Marine carbon dioxide removal (mCDR) has been touted as a potential strategy to reduce atmospheric carbon dioxide levels, with the ocean serving as a sink for human-produced CO₂.

The study, which was recently published in the journal Ocean Science, is the first to measure mCDR in Alaska waters. It focused on kelp farms, which can draw down CO₂ through the process of photosynthesis.

"It's easy to jump on the bandwagon that seaweed is going to change the world, but ultimately we want to be honest to the public," said Amanda Kelley, an associate professor at UAF's College of Fisheries and Ocean Sciences and a contributor to the study. "Really, it's very nuanced, and there are a lot of factors that affect kelp's ability to do that."

Josianne Haag, who led the project as a UAF doctoral student, installed sensors both inside and outside kelp farms in Windy Bay near Cordova and Kalsin Bay on Kodiak Island. From seeding to harvest, hourly data was collected on ocean chemistry, temperature, salinity and oxygen levels.

The two sites had numerous differences, including the type of seaweed being planted, the timing of their growing seasons and the size of the farms. Also, Windy Bay's tides are more extreme than those in Kalsin Bay.

The results were striking and varied. The farms flipped between absorbing and releasing carbon dioxide depending on the amount of sunlight and the time of day. Extreme low tides affected CO₂ levels by flushing groundwater into the area, briefly raising carbon dioxide levels. A film of marine fauna grew on some of the farm equipment in Kalsin Bay, leading to a burst of carbon dioxide production through their respiration.

Overall, the Windy Bay farm slightly reduced nearby atmospheric marine carbon dioxide levels while the Kalsin Bay farm boosted them. Measurements will continue at the farms for at least two more years, but the first season revealed that a kelp farm's recipe for carbon intake and output is surprising and complex.

"It's really not doing much in either direction," Haag said. "The farms aren't necessarily harming anything, but we shouldn't be blowing out of proportion that they're going to save us from climate change."

The study was part of the Mariculture Research and Restoration Consortium project, which is an ongoing effort to look at the impacts and benefits of mariculture in Alaska. Mar ReCon research is funded by the Exxon Valdez Oil Spill Trustee Council.

ADDITIONAL CONTACTS: Josianne Haag, [email protected]; Amanda Kelley, [email protected]

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