Seagrass ecosystems reduce disease risk and economic loss in marine farming production

Seaweed farming comprises over half of global coastal and marine aquaculture production by mass, however the future of the industry is increasingly threatened by disease outbreaks. Nature-based solutions provided by enhancing functions of coinciding species or ecosystems offer an opportunity to increase yields by reducing disease outbreaks while conserving biodiversity. Seagrass ecosystems can reduce the abundance of marine bacterial pathogens, although it remains unknown whether this service can extend to reducing disease risk in a marine resource. Using a meta-analysis of articles published over the past 40 years, we find that 17 known diseases of seaweeds are associated with bacteria that have been previously shown to be lower when associated with seagrass ecosystems. Next, we surveyed over 8,000 individual seaweeds among farms in Indonesia and found disease risk is reduced by 75% when seaweeds are co-cultivated directly within seagrass ecosystems, compared to when seagrass ecosystems were removed. Finally, we estimate that farming seaweed with seagrass ecosystems could increase annual revenue by $292,470 – $1,015,990 USD per km2 from yield loss due to disease reduction, and that ~20.7 million km2 in 107 countries and 34 territories have suitable environmental conditions for farming seaweeds with seagrass ecosystems. These results highlight the global utility for nature-based solutions as an ecologically and economically sustainable management strategy. 

Methods
Fieldwork was conducted at 16 seaweed farms along the southwest coast of Sulawesi in Indonesia, where seaweed is currently co-cultivated in coastal areas directly within intact seagrass ecosystems and where seagrass ecosystems naturally occur, but have been removed. The estimated economic value of disease risk reduction associated with the co-cultivation of seaweed with seagrass ecosystems and global geographic suitability is briefly described in each figure legend. Full materials and methods, including mechanisms of seagrass filtration can be found in the SI Appendix.