Pelagic Sargassum macroalgae can be both an ecologically important habitat in the ocean and a nuisance on the beach. Recent efforts, mainly funded by NASA's Ocean Biology and Biogeochemistry program and Ecological Forecast program, led to the initial understanding of Sargassum biology, abundance distributions, and development of a decision-making tool to track large Sargassum mats in near real-time (see Sargassum Watch System or SaWS, https://optics.marine.usf.edu/projects/saws.html), with SaWS and its associated monthly bulletins being used extensively and routinely by many stakeholders including governmental agencies, environmental groups, private sectors, and the general public. The discovery of the great Atlantic Sargassum belt extending from the west Africa to the Gulf of Mexico, which has been recurrent since 2011, suggests a possible oceanic regime shift where recurrent Sargassum blooms may become the new normal in future years. Other macroalgae blooms have also been reported in other parts of the oceans, emphasizing the importance of studying macroalgae in general. The goal of this project is to improve our understanding of Sargassum physics, biology, and physiology in support of PACE mission goals, with the following objectives:
- Develop PACE-compatible algorithms to characterize Sargassum physics, including color tones, depth, areal density, and biomass density
- Develop PACE-compatible algorithms to understand Sargassum biology, including Sargassum pigment composition, carbon, nitrogen, phosphorous, and growth rate
- Understand Sargassum physiology through characterizing its Sun-induced fluorescence (SIF)
- Work with the NASA PACE SDS team to implement core algorithms to prepare for PACE mission
- Demonstrate the potentials of using PACE-analog data and PACE-compatible algorithms in improving SaWS in order to benefit the user communities
- Explore the possibility of using PACE-analog data to study other types of floating macroalgae (e.g., Ulva) and microalgae (e.g., Noctiluca scintillas, Trichodesmium).
The project will be conducted through field and laboratory measurements, bio-optical modeling, numerical modeling, sensitivity analysis, and algorithm development with particular emphasis on the hyperspectral capacity of PACE. Although the project is mainly focused on science, it has significant implications on management applications. Indeed, based on the currently NASA funded efforts, SaWS is at approximately Application Readiness Level (ARL) 7, with an anticipated ARL 9 by the project end (2021). The proposed work will not change the ARL of SaWS, but will add significant values to improve SaWS, thus contributing directly to the ultimate goal of NASA Applied Science. Furthermore, because of its vast distributions and abundance at scales way beyond previous knowledge, Sargassum is closely related to the Surface Biology and Geology (SBG) theme (subject: macroalgae) from the most recent decadal survey, and remote sensing study of Sargassum has significant implications to both ocean ecology and biogeochemistry (e.g., carbon and nutrient cycles).
We expect the following project outcome to showcase PACE capacity in understanding the role of pelagic Sargassum macroalgae in ocean ecology and biogeochemistry:
- Improved understanding of Sargassum physics, biology, and physiology
- PACE-compatible algorithms to characterize Sargassum physics, biology, and physiology, which can be implemented by NASA SDS and improved upon the launch of PACE. The primary product will be Sargassum biomass density, while the second product will be Sargassum growth rate and/or fluorescence efficiency.
- Demonstration of PACE-unique products to enhance SaWS
- Technical reports, publications, and a sustained system to facilitate the use of NASA PACE data and other data to help make management and research decisions.