Jouanno Julien, Berthet S., Müller-Karger F., Aumont Olivier, Sheinbaum J.
Source
Communications Earth and Environment, 2025,
6 (1), 95 [11 p.]
The proliferation of pelagic Sargassum in the tropical Atlantic since 2011 is causing considerable health and economic concerns as large amounts of this brown alga arrive and accumulate in coastal ecosystems of western Africa and of the greater Caribbean Sea every year. Many hypotheses have been proposed to explain the recurrence of Sargassum blooms since 2011 and their year-to-year variability. Among the hypotheses being debated about the origin and nutrient source to support the blooms are either: a) an increase in nutrient supply to the Atlantic Ocean via continental, or atmospheric inputs, or b) long-distance transport of a seed population during the North Atlantic Oscillation (NAO) event of 2009/2010 and stimulation of blooms in the tropical North Atlantic by nutrient supply primarily due to seasonal vertical mixing of the upper water column. The aim of this study is to address these alternate hypotheses. To this end, interannual numerical simulations (2002-2022) representing the transport, growth, and decay of pelagic Sargassum have been developed at basin scale. Our results confirm the role played by the NAO transport anomaly on the regime shift that occurred in 2010, and the primary role of vertical mixing in the tropical Atlantic as the primary nutrient source for the recurring blooms since 2011.
