The impact of climate change and agricultural waste: The giant algae belt of the Atlantic

In December 2025, an unprecedented natural crisis emerged in the Atlantic Ocean. Researchers at Florida Atlantic University reported that the Great Atlantic Sargassum Belt has reached a record 37.5 million tons.

This giant algae layer extends over an area of about 8,850 kilometers from West Africa to the Gulf of Mexico. Sargassum algae provides habitat for marine life, but its overgrowth is now harmful to ocean ecosystems and coastal economies.

Scientists identify two main causes for this abnormal growth: agricultural fertilizers and wastewater from the Amazon and Congo river basins, which are nourishing the algae. Second, climate change is causing ocean temperatures to rise and wind patterns to change.

The algae now contain 50% more nitrogen than they did in the 1980s, a direct result of human pollution. Algae on beaches decomposes, producing a bad smell and releasing toxic hydrogen sulfide gas that can lead to respiratory issues.

The impact on tourism and the fishing industry is far-reaching. Many Caribbean resorts are now closing because of the algae. Fishermen can’t cast their nets due to a thick layer of algae that is damaging their boats and nets. Scientists are now considering using the algae as a carbon sink.

Sargassum absorbs large amounts of carbon, but when it decomposes, that carbon is released back into the air. Researchers are developing technologies to either sink algae to the deep sea or convert it into organic fertilizer and biofuel. Sea level changes highlight how land pollution can harm large parts of the ocean.