New Drifters Solve a Key Problem in Tracking Sargassum Seaweed Across the Atlantic

University of Miami oceanographer María Josefina Olascoaga and her team have developed a new generation of drifting sensors designed to stay lodged inside mats of Sargassum, the brown macroalgae that has washed ashore in large quantities on Gulf Coast and Atlantic beaches this summer. Earlier drifters, Olascoaga said, tended to become dislodged from the mats, leaving researchers uncertain whether the devices were tracking the seaweed or drifting freely on their own.

The new drifters, developed with the Miami-based aerospace and technology company Altametry, use GPS, color-detection sensors and built-in cameras to confirm they remain attached to a mat, and transmit data on its heading, position and acceleration. The device that has proved key to keeping the drifters embedded is a simple strip of plastic fencing, ordered online, attached to the canister-shaped drifter, according to Altametry chief engineer Candido Hernandez.

The team tested the drifters in Biscayne Bay, in the Rosenstiel School's Air-Sea Interaction Saltwater Tank, which simulates wave and wind conditions, and at Darwin Beach on Virginia Key. An uncrewed Altametry surveillance blimp also rose more than 300 feet above Biscayne Bay to track the drifters and Sargassum mats from the air, staying aloft for about five hours during testing.

Researchers say the next phase will involve embedding the drifters in Sargassum mats for weeks or months to study their long-range transport across the Atlantic. Unlike satellites, which can lose track of a Sargassum mat's continuous path when clouds, sunglint or aerosols interfere, drifters can provide an uninterrupted record of a mat's motion — data researchers say is needed to validate models that predict how Sargassum moves under the combined effects of currents, winds and waves.