By: Carlyn Scott, Science Communications Manager
A brown alga called Sargassum has inundated beaches in the Caribbean since 2011, impacting tourism, harming the health of humans and marine life, and costing local governments millions of dollars per year to clean up.
Scientists have been divided on the causes of the phenomenon known as the Great Atlantic Sargassum Belt (GASB). But a may have identified what drove a tipping point that established this alga in the tropical Atlantic Ocean.
The key drivers were wind, ocean currents, and nutrients, according to the international team of researchers who published the recent study. Specifically, two consecutive years of a strong negative North Atlantic Oscillation (NAO), a shift in atmospheric pressure over the Atlantic that changes circulation and wind patterns, pushed Sargassum into the tropics. There it found warm, nutrient-rich waters, and lots of sunlight, all year-round.
鈥淎t first, the evidence is that just a few patches of Sargassum were being pushed south by winds and currents during this NAO period of 2009-2010,鈥� said co-author Frank Muller-Karger, Distinguished University Professor and biological oceanographer at the 黑料网吃瓜爆料College of Marine Science (CMS). 鈥淏ut these algae patches met the right conditions to grow and perpetuate blooms when they reached the area close to the equator.鈥�
Every year, patches of Sargassum come together in the tropical Atlantic, pushed by the Trade Winds into an area where the ocean is rich in nutrients brought up from deeper waters below, explains Muller-Karger. These Sargassum patches form a new, large population in the region that spans from Africa to the Americas.
Authors of the recent paper in Nature Communications use a computer model that helped them to go into more details and test new scenarios than was possible in a prior study published in . That study first identified the possible i