Scientists struggling to understand this year’s Atlantic Sargassum conundrum

The Great Atlantic Sargassum Belt is a biomass stretching from West Africa to the Gulf of Mexico that contains scattered patches of seaweed. Satellite images captured in February showed an earlier start than usual for such a large accumulation in the open ocean. The seaweed floats on the ocean and reproduces on the water’s surface.

Sargassum originates in a vast stretch of the Atlantic Ocean called the Sargasso Sea, which lies east of Florida and the Caribbean. Four prevailing ocean currents form its boundaries.

Floating sargassum

FLORIDA

How sargassum travels

Surface currents

Miami

Gulf of Mexico

Atlantic Ocean

Havana

CUBA

Cancun

Port-au-Prince

MEXICO

HOND.

NIC.

Caribbean Sea

VENEZUELA

COLOMBIA

As of april 5

john sopinski/the globe and mail, Source: european space agency

Floating sargassum

FLORIDA

How sargassum travels

Surface currents

Miami

Gulf of Mexico

Atlantic Ocean

Havana

CUBA

Cancun

Port-au-Prince

MEXICO

HOND.

NIC.

Caribbean Sea

VENEZUELA

COLOMBIA

As of april 5

john sopinski/the globe and mail, Source: european space agency

Floating sargassum

How sargassum travels

FLORIDA

Surface currents

Miami

Gulf of Mexico

Atlantic Ocean

Havana

CUBA

Cancun

Port-au-Prince

MEXICO

HOND.

NIC.

Caribbean Sea

VENEZUELA

COLOMBIA

As of april 5

john sopinski/the globe and mail, Source: european space agency

The matted brown seaweed stretches for miles across the ocean and provides breeding ground, food and habitat for fish, sea turtles and marine birds, according to the U.S. National Oceanic and Atmospheric Administration.

However, when sargassum piles up on beaches, it quickly decomposes under the hot sun, releasing gases that smell like rotten eggs. It has carpeted beaches on some Caribbean islands such as the Dominican Republic, and Mexico’s Yucatan Peninsula in the spring and summer.

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When sargassum decomposes, it releases ammonia and hydrogen sulphide, which accounts for the rotten-egg stench. Brief exposure isn’t enough to make people sick, but prolonged exposure – especially for those with respiratory issues – can be dangerous, scientists say.

While 2023 appears to be a heavy year for the seaweed, it’s been worse. Scientists estimate there’s more than 10 million metric tons of sargassum in the belt this year, which is slightly less than 2018, a record year.

Scientists aren’t exactly sure, what causes sargassum, in part because it wasn’t closely monitored until 2011.

Experts believe agricultural runoff seeping into the Amazon and Orinoco rivers and eventually the ocean could explain the increased growth. Warming waters likely help the seaweed grow faster.

– Associated Press