Sinking Sargassum

• Published in: Geophysical research letters 2022-09, Vol.49 (17), p.n/a
• Main Authors: Putman, Nathan F., Hu, Chuanmin
• Format: Article
• Language: English
• Subjects: Algae; Atlantic Ocean; Blooms; Coastal ecosystems; Cyclones; Ecological effects; Ecology; Economic importance; Ecosystems; Hurricane tracking; Hurricane tracks; Hurricanes; Mortality; Oceans; Physical factors; Principles; Rafting; remote sensing; Sargassum; Satellites; Sinking; Statistical analysis; Statistical methods; Storms; tropical cyclone; Tropical cyclones
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL100189

Blooms and coastal inundations of pelagic Sargassum have caused major problems to coastal communities and ecosystems throughout the tropical Atlantic over the past decade. Understanding Sargassum growth, movement, and mortality is essential to being able to predict and mitigate these events. In principle, tropical cyclones that occur in this area could have an impact on all three processes. In a recent article, Sosa‐Gutierrez et al. (2022, https://doi.org/10.1029/2021GL097484) investigated the potential impacts of tropical cyclones (TCs) on pelagic Sargassum using satellite‐based Sargassum maps and 86 hurricane tracks during 2011–2020. Their statistical analysis showed an average drop of 40% in Sargassum coverage under TC trajectories, which was attributed to possible sinking of Sargassum. Here, we discuss implications of these findings, and advocate continued research on how storms and other physical factors influence the dynamics of growth, movement, and mortality in this ecologically and economically important macroalgae. Plain Language Summary Pelagic Sargassum in the Atlantic Ocean plays an important role in ocean ecology, yet excessive Sargassum on beaches can have dramatic negative consequences to human communities and coastal ecosystems. Predicting beaching events requires knowledge on how Sargassum grows, moves, and dies. In principle, major storms like tropical cyclones could impact each of these processes. A recent GRL article by Sosa‐Gutierrez et al. (2022, https://doi.org/10.1029/2021GL097484) investigated some of these questions by comparing satellite‐based Sargassum estimates before and after the passage of hurricanes and found substantially decreased Sargassum amounts. Regardless of how much this pattern results from Sargassum sinking, rafts fragmenting, or uncertainties in the satellite‐derived Sargassum maps, storms may have a major impact on Sargassum's distribution and abundance—with important implications for its function in the ecosystem. Key Points The distribution and abundance of a species is the result of the reproduction, mortality, and movement of organisms For marine organisms, like pelagic Sargassum, these three processes can each be strongly impacted by tropical storms Understanding the mechanisms that drive storm impacts will be valuable for predicting Sargassum dynamics and problems like beaching events