Innovative spectral characterisation of beached pelagic sargassum towards remote estimation of biochemical and phenotypic properties

• Published in: The Science of the total environment 2024-03, Vol.914, p.169789-169789, Article 169789
• Main Authors: Fidai, Y.A., Botelho Machado, C., Dominguez Almela, V., Oxenford, H.A., Jayson-Quashigah, P.-N., Tonon, T., Dash, J.
• Format: Article
• Language: English
• Subjects: Coastal management; Macroalgae; Marine ecosystems; Remote sensing; Sargassum
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.169789

In recent years, pelagic sargassum (S. fluitans and S. natans – henceforth sargassum) macroalgal blooms have become more frequent and larger with higher biomass in the Tropical Atlantic region. They have environmental and socio-economic impacts, particularly on coastal ecosystems, tourism, fisheries and aquaculture industries, and on public health. Despite these challenges, sargassum biomass has the potential to offer commercial opportunities in the blue economy, although, it is reliant on key chemical and physical characteristics of the sargassum for specific use. In this study, we aim to utilise remotely sensed spectral profiles to determine species/morphotypes at different decomposition stages and their biochemical composition to support monitoring and valorisation of sargassum. For this, we undertook dedicated field campaigns in Barbados and Ghana to collect, for the first time, in situ spectral measurements between 350 and 2500 nm using a Spectra Vista Corp (SVC) HR-1024i field spectrometer of pelagic sargassum stranded biomass. The spectral measurements were complemented by uncrewed aerial system surveys using a DJI Phantom 4 drone and a DJI P4 multispectral instrument. Using the ground and airborne datasets this research developed an operational framework for remote detection of beached sargassum; and created spectral profiles of species/morphotypes and decomposition maps to infer biochemical composition. We were able to identify some key spectral regions, including a consistent absorption feature (920–1080 nm) found in all of the sargassum morphotype spectral profiles; we also observed distinction between fresh and recently beached sargassum particularly around 900–1000 nm. This work can support pelagic sargassum management and contribute to effective utilisation of the sargassum biomass to ultimately alleviate some of the socio-economic impacts associated with this emerging environmental challenge. [Display omitted] •New operational framework to detect beached pelagic sargassum•Spectral and airborne data from sargassum beaching events in Barbados and Ghana•Spectral profiles of three morphotypes and fresh and old beached sargassum•Fresh and old sargassum are spectrally distinct.•Estimation of biochemical composition of pelagic sargassum from spectra