Seaweed Aquaculture: Optimizing growth rate, photosynthetic efficiency, and bromoform concentration in Asparagopsis taxiformis, a climate change fighting algae

Project Number
Project Date Range
Funding Agency
National Oceanic and Atmospheric Administration (NOAA)
Focus Area(s)
Sustainable Fisheries and Aquaculture

Carbon dioxide (CO2) is often the focus of climate change mitigation efforts, although methane is a far more potent greenhouse gas, having around 28 times more warming potential than CO2. Reducing methane production has become a focal point for governments looking to reduce their greenhouse gas emissions. Agriculture is a leading source of human-caused methane emissions, with a significant percentage produced by cattle.

There has been a growing body of research exploring alternative livestock feeds for the purpose of reducing the amount of methane released by cattle. Of these, supplementation of around one to two percent of a cow’s diet with the red alga Asparagopsis taxiformis has been the most successful, reducing methane output by up to 90%.

While Asparagopsis has a near-global coastal distribution, this project focused on lineages of the alga that grow in California. Researchers conducted growth experiments on strains of Asparagopsis collected from different regions around Southern California. The purpose of these experiments was to understand how variables such as temperature, nutrient concentration, light intensity, and CO2 concentration affect the growth and health of the algae. The project sought to find conditions which optimize Asparagopsis growth and the production of bromoform - the chemical responsible for reducing methane in cows.

The project results as a whole signify that through environmental control and addressing limiting factors, significant increases in biomass production can be achieved, making A. taxiformis a viable species for large-scale cultivation. The results show that given the correct environmental condition, the bromoform concentration of A. taxiformis can be maximized in unison with high growth rates. This will be critical in our future ability to
mass-produce A. taxiformis as a cow feed supplement since the reduction in methane emissions from cows is proportional to the amount of bromoform present in the A. taxiformis.

The results will both lead to an increased availability of biomass to further the trials on the safety and long-term effects of consumption by cows and improve the sustainability and efficiency of the dairy and beef industries.

Principal Investigators
Hannah M. Resetarits
University of California, San Diego, Scripps Institution of Oceanography
Co-principal Investigators
Jennifer Smith
University of California, San Diego, Scripps Institution of Oceanography