THIS PROPOSAL ADDRESSES TWO TOPICS OF THE NNH15ZDA001N-OBB RFP: TOPIC 2.1 (OCEAN ECOLOGY ESPECIALLY TO PREPARE FOR THE PACE MISSION) AND TOPIC 2.4 (SUCCESSOR STUDIES OF PREVIOUSLY OBB-FUNDED PROJECTS).PELAGIC SARGASSUM MACROALGAE SERVE AS AN ECOLOGICALLY IMPORTANT HABITAT FOR MANY MARINE ANIMALS WHILE EXCESSIVE SARGASSUM BEACHING HAS BECOME AN INCREASING NUISANCE SINCE 2011. SARGASSUM MAY ALSO AFFECT OCEAN'S BIOGEOCHEMISTRY THROUGH MODULATING NUTRIENT CYCLES AND RELEASING COLORED DISSOLVED ORGANIC MATTER. HOWEVER TO DATE EXCEPT FOR A HANDFUL OF STUDIES OUR KNOWLEDGE IN THESE AREAS IS ONLY NEXT TO NIL.PREVIOUS MAPPING EFFORTS BASED MAINLY ON MERIS MEASUREMENTS SHOWED BLOOM PATTERNS IN THE INTRA-AMERICAS SEA (IAS). HOWEVER THESE PRELIMINARY RESULTS ARE SUBJECT TO REVISIT BECAUSE OF THE SIMPLE METHODS USED IN THE ESTIMATES AND BECAUSE OF LACK OF MERIS COVERAGE AFTER APRIL 2012. FURTHERMORE THE UNPRECEDENTED SARGASSUM BEACHING EVENTS IN THE CARIBBEAN IN 2015 CALLS FOR A BETTERUNDERSTANDING OF ITS LONG-TERM TREND IN BOTH DISTRIBUTION AND ABUNDANCE.TWO PROJECTS HAVE BEEN FUNDED BY THE NASA OBB PROGRAM (NNX13AD08G NNX14AL98G) TO ASSESS THE DEEPWATER HORIZON OIL SPILL IN THE NE GULF OF MEXICO (GOM) AND TO PROVIDE NEAR REAL-TIME IMAGERY TO HELP TRACK SARGASSUM RESPECTIVELY. THESE FUNDED PROJECTS LED TO GROUND-BREAKING WORK OF USING LANDSAT AND MODIS TO MAP SARGASSUM WITH SIGNIFICANT PROGRESS BEING MADE TO DATE FOR EXAMPLE THE DISCOVERY OF THE GREAT ATLANTIC SARGASSUM BELT. ONE CONCLUSION FROM THESE RESULTS IS THAT SARGASSUM ABUNDANCE AND BIOMASS MAY HAVE BEEN SIGNIFICANTLY UNDERESTIMATED IN THE PAST.BASED ON THESE PRELIMINARY RESULTS THE ULTIMATE GOAL IS TWO-FOLD: TO STUDY SARGASSUM DISTRIBUTION AND ABUNDANCE AS WELL AS TO UNDERSTAND THE DRIVING FACTORS USING EXISTING SENSORS AND ENVIRONMENTAL VARIABLES AND TO DESIGN AND TEST ALGORITHMS SPECIFICALLY FOR PACE AND EXISTING MULTI-BAND SENSORS. SPECIFICALLY THE PROJECT HAS THE FOLLOWING OBJECTIVES:1) DESIGN IMPLEMENT AND TEST PACE-COMPATIBLE ALGORITHMS TO DETECT AND QUANTIFY SARGASSUM FROM WHICH ALGORITHMS TO USE EXISTING MULTI-BAND SENSORS ARE ALSO IMPROVED2) PROVIDE THE BEST ESTIMATES OF TOTAL SARGASSUM BIOMASS (AND PIGMENTS AND C N P FE) AND DISTRIBUTIONS THEIR SEASONALITY INTERANNUAL VARIABILITY AND LONG-TERM TREND WITH UNCERTAINTY ESTIMATES3) DETERMINE DOMINATE ENVIRONMENTAL FACTORS (NUTRIENT AVAILABILITY WEATHER FLUCTUATIONS OCEAN MIXING AND CIRCULATION ETC) THAT DRIVE THE INTER-ANNUAL VARIABILITY AND LONG-TERM TREND IN THE DISTRIBUTION PATTERNS4) DOCUMENT HOW SARGASSUM POPULATIONS ARE CONNECTED BETWEEN THE GOM TROPICAL ATLANTIC AND OTHER REGIONS OF THE IAS5) IMPROVE EXISTING DATA PRODUCTS IN THE CURRENT SARGASSUM WATCH SYSTEM TO BETTER SERVE THE COMMUNITY AND PROVIDE MANAGEMENT DECISION SUPPORT.THE PROJECT WILL BE CONDUCTED THROUGH MULTI-SENSOR REMOTE SENSING CAREFULLY DESIGNED FIELDWORK LABORATORY MEASUREMENTS AND INTEGRATED DATA ANALYSIS BY AN INTER-DISCIPLINARY TEAM. THE PROJECT WILL LEVERAGE ON CURRENTLY FUNDED GOMRI CRUISE SURVEYS AND CRUISE SURVEYS BY OUR PARTNERS TO SAVE SHIP COST.THE PROJECT WILL MAKE SIGNIFICANT CONTRIBUTIONS TO NASA GOALS AND IN PARTICULAR TO THIS RFP FOR TWO REASONS: 1) IT IS PERFECTLY SUITABLE TO ADDRESS QUESTIONS SPECIFIED IN TOPIC 2.1 AS IT WILL NOT ONLY PROVIDE FOR THE FIRST TIME THE LONG-TERM TREND OF SARGASSUM ABUNDANCE BUT ALSO LEAD TO BETTER UNDERSTANDING OF THE ENVIRONMENTAL FACTORS DRIVING THE SHORT-TERM CHANGES AND LONG-TERM TREND.FURTHERMORE CURRENT SENSORS (MODIS AND LANDSAT) AND FUTURE SENSORS (PACE) ARE USED NOT ONLY FOR RESEARCH BUT ALSO TO BETTER INFORM MONITORING MANAGEMENT AND DECISION AND POLICY MAKERS. 2) IT IS BASED ON RESULTS FROM PREVIOUSLY OBB-FUNDED RESEARCH WHICH WILL MAKE SIGNIFICANT ADVANCEMENT FROM THE RESULTS OBTAINED TO DATE. THE PROJECT IS ALSO RELEVANT TO OTHER NASA THEMES FOR EXAMPLE ECOLOGICAL FORECASTING BIODIVERSITY AND APPLIED SCIENCE.