Alaska Kelp Farms Show Mixed Results for Carbon Removal, Study Finds
Kelp farms in Alaska have shown highly variable effects on local carbon dioxide levels, with new research suggesting that their climate benefits may be far less predictable than previously assumed.
A study led by the University of Alaska Fairbanks has found that marine carbon dioxide removal (mCDR) potential from kelp cultivation depends heavily on local environmental conditions, with some sites slightly reducing carbon dioxide in surrounding waters while others appear to increase it.
The research examined two kelp farms in the Gulf of Alaska during the 2023–2024 growing season, measuring carbon dioxide flux alongside ocean chemistry, temperature, salinity and oxygen levels. The study is the first of its kind in Alaska waters and was published in the journal Ocean Science.
Researchers found sharply contrasting outcomes between the two sites. One kelp farm showed a modest net reduction in local carbon dioxide levels, while the other recorded a net increase over the same period, highlighting the complexity of biological carbon removal in marine environments.
Lead researcher Amanda Kelley of the University of Alaska Fairbanks said the results challenge simplified assumptions about seaweed’s role in climate mitigation. She noted that kelp’s ability to absorb carbon is influenced by a wide range of factors, including sunlight, tidal patterns and local ecosystem activity.
The study tracked conditions at kelp farms in Windy Bay near Cordova and Kalsin Bay on Kodiak Island. Sensors installed throughout both sites recorded hourly data across the full growing season, capturing rapid fluctuations in carbon dioxide levels linked to environmental changes.
Researchers observed that carbon dioxide levels at the farms shifted throughout the day, alternating between periods of absorption and release depending on light availability and biological activity. In some cases, extreme low tides caused groundwater influxes that temporarily increased carbon dioxide concentrations in surrounding waters.
Biological processes also played a role. In one location, marine organisms that accumulated on farming equipment contributed to increased respiration, which in turn raised local carbon dioxide levels.
The findings suggest that kelp farms do not operate as consistent carbon sinks, but rather as dynamic systems where carbon uptake and release can fluctuate significantly over short timescales. One of the farms studied showed a slight net reduction in carbon dioxide, while the other showed a net increase.
Researcher Josianne Haag, who led the fieldwork as part of her doctoral studies, said the results indicate that kelp farming should not be overestimated as a climate solution, despite its potential role in broader marine carbon strategies.
The study concludes that while kelp cultivation may offer some carbon removal benefits under certain conditions, its overall impact is highly site-specific and influenced by complex environmental interactions. Researchers emphasised the need for continued long-term monitoring to better understand when and where marine carbon removal strategies may be effective.
The work forms part of a broader research initiative into mariculture systems and their environmental impacts in Alaska, supported through the Mariculture Research and Restoration Consortium.
