From West Africa to the Caribbean, a brown ribbon now sprawls across the Atlantic. In May, satellites estimated roughly 37.5 million metric tons of floating sargassum, ZME Science reports, a record-setting mass that scientists say is reshaping coasts and commerce.

What began as seasonal patches has become the Great Atlantic Sargassum Belt, a moving ecosystem—and a mounting challenge for people and wildlife.

The Great Atlantic Sargassum Belt spans thousands of miles.

Why It’s Growing—and Why It Matters

Sargassum thrives when warmth and nutrients align. Researchers point to nutrient inputs from land—agricultural runoff, wastewater, and atmospheric deposition—as key accelerants that now push growth well beyond the historically lean Sargasso Sea, according to ZME Science. Once adrift, ocean currents ferry mats through the Gulf and into the wider Atlantic, where they can persist, recycle nutrients within the raft, and expand.

At sea, the floating canopy shelters fish, invertebrates, and juvenile turtles. Onshore, the story flips. Rotting drifts release hydrogen sulfide, irritate eyes and lungs, and overwhelm cleanup crews. Caribbean destinations from the Mexican Caribbean to Barbados and the Dominican Republic have watched summer beach seasons collide with heavy strandings, reports TravelPulse.

Nutrient runoff from agriculture fuels its growth.

Trouble for Tiny Travelers

For sea turtle hatchlings, seconds count. New experiments on Florida beaches show that low piles of sargassum can more than double the time it takes hatchlings to reach the surf; higher piles stop some entirely. The tangled thicket flips turtles repeatedly, burning precious time and exposing them to predators and heat, according to BBC Wildlife’s Discover Wildlife.

Scientists measured delays across leatherback, loggerhead, and green turtles. In some trials, loggerheads slowed by more than 170% in heavier seaweed, while leatherbacks and greens suffered similar slowdowns. Glucose readings suggested short-term energy stores remained stable, but time on open sand—not blood sugar—proved the real risk, the teams told Earth.com.

Warmer waters create ideal conditions for sargassum expansion.

Tourism’s Summer Squeeze

Sargassum season often spans March through October, with the thickest landings from May to August. That window overlaps peak vacations, and even diligent cleanup—tractors at sunrise, barriers offshore—struggles to keep pace. Travelers still come, but the guest experience can hinge on daily wind, currents, and local response capacity, notes TravelPulse. The broader fix, experts say, rests upstream: curb nutrient runoff and improve wastewater treatment to dull the bloom’s fuel.

What Comes Next

The belt is now an annual player, not an anomaly. Forecasting has improved, yet weekly conditions remain patchy and local. Coastal cities weigh cleanup costs, hoteliers chase clear-water pockets, and conservation teams work around nesting calendars. Meanwhile, the open-ocean mats continue to function as habitat even as shoreline drifts strain infrastructure, ZME Science reports.

For hatchlings, minor barriers become existential threats. For beach towns, a natural plant becomes an economic headache. And for the Atlantic, a new normal is taking shape—long, mobile, and tied to choices made far inland[.](https://www.travelpulse.com/voices/opinions/the-caribbean-s-biggest-summer-problem-continues)