Floating mats of pelagic Sargassum macroalgae serve as an ecologically important habitat for many marine animals and therefore are regarded by the Sargasso Sea Commission as “the golden floating rainforest of the Atlantic Ocean.” On the other hand, excessive Sargassum beaching has become an increasing nuisance in the Caribbean since 2011. Recent efforts, mainly funded by NASA, led to the ground-breaking work of using Landsat and MODIS to map Sargassum, and to the establishment of a prototype decision-making tool to track large Sargassum mats in near real-time, the Sargassum Watch System (SaWS, http://optics.marine.usf.edu/projects/saws.html). Yet several improvements are required to maximize its full potential. Thus, based on the existing infrastructure (hardware, software, personnel) and the established prototype SaWS, the goal of this project is to further develop and improve SaWS in its data products and in both its long-term and short-term forecasting capacity to better serve the community. Specifically, the project has the following objectives: 1) Expand SaWS coverage to include waters off Africa and Brazil, where Sargassum beaching has been reported but currently there is no near real-time imagery support 2) Determine Sargassum distribution and abundance as well as their seasonality, inter-annual variability, and long-term trend with uncertainty estimates for the IAS and other regions 3) Develop a forecasting model to predict Sargassum blooms in different ocean basins, and determine likelihood of Sargassum beaching for each Caribbean nation or region; 4) Establish short-term forecasting capacity in predicting Sargassum transport, and implement such a capacity for near real-time use in the SaWS 5) Generate and distribute weekly and biweekly composites of value-added products in the SaWS to avoid arbitrary interpretation of imagery by untrained users 6) Increase the user base for SaWS in order to maximize the potential of NASA data for community use 7) Make SaWS quasi-operational and sustainable to benefit society, and make it a template for other regions to monitor and respond to macroalgae blooms. The project will be conducted through multi-sensor remote sensing, statistical analysis, modeling, image processing, computer programming, and interactions and collaborations with various user groups. Indeed, based on previous efforts, SaWS is at approximately ARL 4 already, with some components of ARLs 5 – 9 also implemented. However, without dedicated effort and innovations SaWS is currently at its maximum capacity. The project will make significant improvements in this prototype decision-making tool through achieving the 7 specific objectives, thus contributing directly to the ultimate goal of NASA Applied Science. We expect the following outputs: 1) Enhanced SaWS to distribute new value-added data products in near real-time to help make near real-time decisions (beaching management, tourism, cruise planning, etc) through improved short-term forecast of Sargassum transport and beaching potentials; 2) Long-term spatial-temporal distributions of Sargassum abundance in the IAS and other regions with uncertainty estimates and improved understanding of their climate and environmental controls, which will provide baseline data to help implement/improve Sargassum management plans; 3) Long-term forecast of likelihood of Sargassum blooms with several months of lead time to inform relevant stakeholders for long-term planning; 4) Technical reports, publications, and a sustained system to facilitate use of NASA data to help make management and research decisions. The end users of the improved SaWS range from Federal and state agencies to educational institutions, environmental groups, and private entities. These may include: National Marine Fisheries Service (NMFS), the Sargasso Sea Commission, airline companies, beach management agencies, and tourism industry.