As the United States marine seaweed aquaculture industry develops, there is immense opportunity to site farms in locations that maximize the co-benefits of seaweed aquaculture, including nutrient assimilation. Se aweed aquaculture is capable of removing large quantities of nitrogen and phosphorus from coastal ecosystems, yet seaweed has gained little traction for its potential role in targeted nutrient assimilation. In the U.S., nitrate loading over the past 20 years has been relatively constant at an exceedingly high input level, while phosphate loading has continued to increase
. In May 2019, phosphate loads to the Gulf of Mexico were 49% above the long-term average, leading to a historically large dead zone
. Current management systems in the U.S. do not fully address the large and growing nutrient pollution problem
, and the U.S. Environmental Protection Agency is actively seeking new management strategies . Here, w e determine the optimal siting locations for seaweed aquaculture with the objective of maximizing the co-benefit of reducing nutrient pollution in the U.S.
Our analysis identifies pollution “hotspots” in coastal waters, where anthropogenic nutrient loading is high compared to natural nutrients, and then assesses seaweed aquaculture suitability in these areas to estimate the assimilation capacity of seaweed farming. Finally, we will corroborate our U.S. wide results with a fine scale case study in the Gulf of Mexico, where we couple a seaweed growth model with highly resolved pollution data. We show that targeted seaweed aquaculture development in key locations, such as the Florida Gulf and much of the Atlantic Coast, can be used to successfully assimilate anthropogenic nutrient pollution. By contrast, naturally high nutrient areas are unlikely to benefit from seaweed aquaculture’s nutrient assimilation services. These findings underscore the opportunity to site seaweed aquaculture to maximize co-benefits and provide important ecosystem services, rather than merely fitting farms into suitable marine space.