Mapping Algae Across the World's Oceans
The planet's ocean surfaces are changing. For the first time, scientists have used artificial intelligence to measure the global spread of floating algae. The work was led by the University of South Florida together with the U.S. National Oceanic and Atmospheric Administration (NOAA), and the findings appeared in Nature Communications. More than 1.2 million satellite images taken between 2003 and 2022 were examined.
What the Data Shows
A deep learning model split the ocean into 13 geographic zones and looked at five types of algae. Altogether, algal blooms covered 43.8 million square kilometers. On average, the area of microalgae films expanded by 1% each year. Macroalgae showed an even sharper trend: in the tropical Atlantic and the western Pacific, macroalgae growth rose at an annual rate of 13.4% starting in 2008.
Beginning in 2010, researchers observed repeated, large-scale blooms of sargassum and green algae in the Yellow Sea, the East China Sea, and the Atlantic Ocean. They connect these events to:
- warmer water temperatures;
- shifts in ocean currents;
- higher nutrient loads entering the sea through coastal runoff.
Far from shore, large algae patches can serve as habitats for fish. But when they pile up along coastlines, decaying biomass can damage local ecosystems, pose health risks to people, and hurt tourism and coastal economies.
This assessment is an important step toward understanding how ocean ecosystems are responding to global pressures. The team plans to continue investigating the regional drivers behind this shift.
Because these algae expansions affect marine biodiversity and industries tied to fishing and tourism, their consequences may be significant. Further research could provide the knowledge needed to manage blooms and reduce environmental and social harm.
The impacts of changing ocean conditions are not limited to algae; they also affect other celestial bodies. For instance, recent studies have highlighted how the freezing of water in Europa's ice cracks can significantly hinder access to subsurface oceans. Understanding these phenomena across different environments is crucial for comprehending the broader implications of climate change on marine ecosystems.