Significant blooms of the brown seaweed Sargassum in the tropical Atlantic have been taking place since 2011, impacting tourism in the Caribbean. A more general observation is that between 2003 and 2022, macroalgal mats and microalgal scum have expanded around the globe. A recent study looked at the rise of macroalgae blooms across the globe over the past two decades.
Researchers at the University of South Florida, the National Oceanic and Atmospheric Administration, and several other institutions used artificial intelligence to scan 1.2 million satellite images of the oceans, focusing on 13 specific zones and five types of algae.
The conclusions were that blooms of macroalgae increased by 13.4% per year in the tropical Atlantic and Western Pacific, with the most dramatic increases occurring after 2008. The cumulative size of these seaweed blooms reached 16.9 million square miles, roughly the size of North and South America combined. The bloom expansions are a result of both direct human activities like nutrient runoff into the ocean, and the impact of climate change driving ocean warming.
The presence of this seaweed is a double-edged sword. In open water, it can provide critical habitat for marine life and can serve as a nursery for many fish species. But once it reaches coastal waters, the decaying biomass can cause considerable harm to tourism, local economies, and the health of people and marine life.
