“A New Study Reveals the Triggering Factor Behind Massive Sargassum Blooms”
Since 2011, massive sargassum strandings have disrupted marine ecosystems and coastal communities in the tropical Atlantic. A recent study, published in Communications Earth & Environment, highlights a key element behind this phenomenon: an extreme North Atlantic Oscillation (NAO) event in 2009-2010.
An Ecological Shift in 2010
The study demonstrates that this exceptional climatic event altered ocean currents, transporting sargassum from the North Atlantic subtropical gyre to the tropical Atlantic. This shift marked a true ecological tipping point, explaining the massive presence of sargassum in this region since 2011.
Photo: Mady Aïssata Merine
The Role of Nutrients: A Misconception Corrected
Contrary to popular belief, this study confirms that sargassum blooms are not directly caused by nutrient inputs from rivers (Amazon, Orinoco, Mississippi, Niger, etc.) or Saharan dust. Instead, sargassum obtains most of its nutrients from seasonal vertical mixing in tropical waters, which brings essential elements from the ocean depths.
Why Do These Strandings Happen Every Year?
Several factors contribute to the annual recurrence of sargassum blooms:
- Favorable conditions in the tropical Atlantic (temperature, sunlight, available nutrients).
- Sargassum retention under the Intertropical Convergence Zone (ITCZ) during winter, ensuring its survival and proliferation the following year.
- Transport by ocean currents, dispersing the algae towards the Caribbean, West Africa, and the Gulf of Mexico.
What Is the Connection to Climate Change?
Although this study identifies the 2009-2010 NAO event as the trigger, it also raises questions about the impact of climate change. Rising ocean temperatures could alter sargassum dynamics and influence its future distribution.
A Breakthrough in Understanding the Phenomenon
This discovery challenges previous hypotheses about the origins of sargassum blooms and emphasizes the importance of ocean currents in their regulation. It also helps direct research toward more accurate predictive models to anticipate strandings and better manage this ecological crisis.
➡️ At Sargassum Monitoring, we will continue to track scientific advancements and share essential information to understand and combat this issue.
This summary is based on the original study by Jouanno, J., Berthet, S., Muller-Karger, F., et al. An extreme North Atlantic Oscillation event drove the pelagic Sargassum tipping point, published in Communications Earth & Environment (Nature Portfolio). The full article is available under the Creative Commons BY-NC-ND 4.0 license at this link: https://rdcu.be/d9vC3