Abstract

Sargassum influxes have major negative impacts on the Caribbean. Uncontrollable at the source, local communities are trying to lessen the impacts through biomass collection and valorization. A hurdle for valorization is the large fluctuation and seasonality in Sargassum influxes. This hinders timely collection and valorization planning at yearly to weekly level. Sargassum aquaculture could flatten this fluctuation, storing excess biomass from high influx days and providing Sargassum on days with low or no availability all year long. Hence, Sargassum farms could enable communities to better control the Sargassum influx and together with protective barriers avoid detrimental inundation events. Companies could be able to commit to larger offtake contracts use their machinery more efficiently, and give more stable employment. However, past attempts have shown that Sargassum is difficult to domesticate in situ. We designed, built, and tested a 150 m2 stationary aquafarm prototype in Mt. Wynne Bay, St. Vincent. We were able to retain Sargassum for 1 month while monitoring growth, health, loss of Sargassum and environmental parameters. We observed growth of healthy Sargassum in the aquafarm compared to wild Sargassum. The farm impacted locally the abiotic properties, by increasing the surface water temperature and surface dissolved oxygen content within the aquafarm. Furthermore, we observed hundreds of juvenile and some predatory fish inside and around the farm. As the fish community matured, spear fishermen used it regularly as a fishing location. To our knowledge, this was the first Sargassum domestication attempt on a scale of >10 m2, and our study shows that it was successful. The abiotic and biotic environment changes seen in the farm were similar to observed changes caused by wild Sargassum mats in the open ocean