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Chuanmin Hu
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Optical Oceanography, University of South Florida

ROSES Proposal

Deciphering Sargassum Physics, Biology, and Physiology through PACE Measurements: Implications to Ocean Ecology, Biogeochemistry, and Management Decision Support (2020)

Co-Is: Gustavo Jorge Goni, NOAA Atlantic Oceanographic and Meteorological Laboratory; Brian Lapointe, Florida Atlantic University

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.

Applied Research Topic

Various types of floating macroalgae and floating microalgae have been reported in global oceans and lakes, including Ulva, Sargassum, Noctiluca, cyanobacteria (e.g., microcystics, Trichodesmium), among others. While detecting them using multi-band sensors (e.g., MODIS, VIIRS, OLCI) is possible with some a priori knowledge of the local environment, fingerprinting their types spectrally is more difficult. The hyperspectral capacity of PACE should make it possible to perform spectral diagnostics of their unique spectral features due to various pigment absorptions and backscattering properties. Through using simulated data and data collected by prototype sensors (HICO, DESIS, etc), the project will develop algorithm for spectral discrimination of floating algae and organisms/materials for the regions of the eastern Gulf of Mexico, Florida Straits, and South Atlantic Bight. In addition to floating algae, other floating organisms or materials (e.g., oil slicks, pumice rafts, large plastic patches) can also be identified spectrally through PACE measurements.

Significance

Improved detection and species discrimination of floating algae can be used by Federal and state agencies such as the United States Environmental Protection Agency (USEPA) the Department of Environmental Protection (DEP), and the Department of Health (DOH) to prepare mitigation efforts for macroalgae and cyanobacterial blooms. Further, this information can be helpful for coastal resource managers to prepare mitigation efforts for massive macroalgae beaching events. Lastly, boaters and beach goers can indirectly benefit from detection and discrimination of floating algae through increased awareness and improved ecological planning.

Why PACE

PACE has enough spectral bands in the 380 - 1000 nm spectral region and in the shortwave infrared spectral region (1.2 and 1.6 μm) to spectrally differentiate and quantify various types of floating algae and organisms/materials. The hyperspectral capacity of PACE should make it possible to perform spectral diagnostics of their unique spectral features due to various pigment absorptions and backscattering properties.

End User(s)

Florida Fish and Wildlife Conservation Commission
US Environmental Protection Agency
Ocean Ecologists & Researchers

Publications

Hu, C. (2009). A novel ocean color index to detect floating algae in the global oceans. Remote Sens. Environ. 113 :2118 :2129, DOI: https://doi.org/10.1016/j.rse.2009.05.012.

Hu, C., D. Li, C. Chen, J. Ge, F. E. Muller-Karger, J. Liu, F. Yu, and M-X He (2010). On the recurrent Ulva prolifera blooms in the Yellow Sea and East China Sea. J. Geophys. Res. 115, C05017, DOI: 10.1029/2009JC005561.

Qi, L., C. Hu, K. MIkelsons, M. Wang, V. Lance, S. Sun, B. B. Barnes, J. Zhao, and D. V. der Zande (2020). In search of floating algae and other organisms in global oceans and lakes. Remote Sens. Environ., 239, 111659, DOI: https://doi.org/10.1016/j.rse.2020.111659.

Read about an Early Adopter project that is related to Chuanmin Hu's SAT work ►

Sargassum collected along coastlines, as shown here in Bavaro, Punta Cana

Too much Sargassum can present challenges for marine life and becomes problematic when it collects along coastlines, as shown here in Bavaro, Punta Cana (Dominican Republic)

Sargassum density in July 2018. Scientists used NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua satellites to discover the Great Atlantic Sargassum Belt (GASB), which started in 2011. It has occurred nearly every year and often stretches from the west coast of Africa to the Gulf of Mexico. (Map courtesy of NASA Earth Observatory. Data provided by Mengqiu Wang and Chuanmin Hu, USF College of Marine Science)

Microscope image of Noctiluca, a marine dinoflagellate. It is an HAB species because of its ability to deplete oxygen levels in the water and clog other organisms’ gills.(Image courtesy of Bigelow Laboratory for Ocean Science and Phytopia)

Science Meeting Presentations (2)

PACE Measurements of Sargassum Macroalgae

Hu, C. (06-Oct-21)

PDF (7.4 MB)

PACE Measurements of Sargassum macroalgae

Hu, C., Goni, G.J., and Lapointe, B. (03-Jun-20)

PDF (618 KB)