Tracking Sargassum in the Caribbean: the design, deployment, and validation of a low-cost surface drifter

Abstract

This thesis presents the development of a low-cost surface drifter designed to track and monitor the abundant Sargassum seaweed in the Caribbean. The phenomenon of the Great Atlantic Sargassum Belt (GASB), inundating coastlines in the northern equatorial Atlantic and Gulf of Mexico, has raised concerns due to its negative impacts on marine ecosystems, coastal communities, and tourism. The introduction section provides background information on the arrival of Sargassum in the Caribbean and its ecological significance. One of the key motivations behind the drifter’s development is the potential use of Sargassum as a feedstock for biofuel production. A comprehensive literature review assesses the feasibility of utilizing Sargassum for biofuels, taking into account infrastructure, economics, and scientific challenges. Although Sargassum holds promise as a renewable biomass source, several hurdles must be addressed, including consistent biomass production, processing techniques, and lack of industrial-scale biofuel plants using macroalgae. The core of the thesis is dedicated to the surface drifter development and field trials. Iterative trials are conducted to design a drifter that entangles with Sargassum, providing in situ movement data to complement remote sensing and modeling efforts. The drifter’s design is optimized to mimic Sargassum rafts, and successful deployments off the coast of Puerto Rico demonstrate the potential for effective tracking. The drifter’s association with Sargassum rafts is validated through satellite imagery and wind and current data. In parallel, a low-cost chemical sensing drifter is introduced in the thesis. This advanced drifter iteration incorporates self-validation mechanisms for Sargassum entanglement and enables the measurement of dissolved gases. The chemical sensing capabilities enhance the understanding of Sargassum rafts’ dynamics and their environmental impact. The thesis concludes by summarizing the key findings and implications of the research. The low-cost surface drifters have shown promising potential for tracking Sargassum and studying its movement patterns within the GASB. The drifter’s effectiveness in entangling with Sargassum provides valuable insights into the seaweed’s behavior and could help improve existing remote sensing and modeling techniques.