Huge blankets of seaweed are smothering coastlines from the Caribbean to Mexico

Some 27 million metric tons of self-sustaining sargassum have been recorded in the Atlantic, Caribbean and Gulf of Mexico in July, according to a report released Friday by the University of South Florida's Optical Oceanography Lab.

Some 27 million metric tons of self-sustaining sargassum have been recorded in the Atlantic, Caribbean and Gulf of Mexico in July, according to a report released Friday by the University of South Florida's Optical Oceanography Lab.