Journal Article

Sargassum Enrichment in Mesoscale Eddies of the Great Atlantic Sargassum Belt

Zhang, Yingjun, Barnes, Brian B., Hu, Chuanmin, McGillicuddy, Dennis J.

2025

Overview

Pelagic Sargassum has increased dramatically in the past decade, primarily in the annually recurrent Great Atlantic Sargassum Belt (GASB) that extends from the coast of West Africa to the Gulf of Mexico. Using satellite observations of Sargassum density and mesoscale eddies from 2011 to 2023, we investigate whether more Sargassum can be found in mesoscale eddies. Cyclonic eddies were found to contain 6%–47% more Sargassum (relative to eddy‐free waters) across all selected regions within the GASB, with the highest Sargassum density in their inner cores (<0.5 eddy radius). Impacts of anticyclonic eddies were weaker and varied between regions. In addition, Sargassum enrichment tended to be higher in eddies with greater size or amplitude, such as the North Brazil Current rings and those in the Caribbean Sea. These findings may inform Sargassum mitigation strategies, for example, through physical removal in targeted locations. Plain Language Summary Over the past decade, floating brown seaweed Sargassum has increased dramatically across the Atlantic Ocean, forming a massive Sargassum belt that stretches from the coast of West Africa to the Gulf of Mexico. Using satellite observations of Sargassum and mesoscale eddies (a type of swirling ocean current) from 2011 to 2023, we investigate whether more Sargassum can be found in mesoscale eddies. Cyclonic (counterclockwise) eddies were found to contain 6%–47% more Sargassum (relative to eddy‐free waters) across all selected regions within the belt, with the highest Sargassum density in their inner cores (<0.5 eddy radius). The findings with anticyclonic (clockwise) eddies were less consistent. In addition, Sargassum enrichment tended to be higher in eddies with greater size or amplitude. These findings may inform Sargassum mitigation strategies, for example, through physical removal in targeted locations. Key Points Sargassum densities in cyclonic eddies (CEs) were 6%–47% higher than in eddy‐free waters, while results varied with anticyclonic eddies The inner cores of CEs (<0.5 eddy radius) generally showed the highest enrichment of Sargassum North Brazil Current rings and mesoscale eddies in the Caribbean Sea play an important role in Sargassum enrichment

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Algae / Amplitude / Amplitudes / Brazil Current / Cores / Current rings / Density / Eddies / Enrichment / Great Atlantic Sargassum Belt / Mesoscale eddies / Mesoscale phenomena / Ocean circulation / Ocean currents / Oceans / pelagic Sargassum / Sargassum / Satellite observation / Satellites / Seaweeds / Swirling / Vortices