Implementation of a Sargassum Seaweed Tracker for the Caribbean

Abstract

Sargassum seaweed floats, clumps together and can stretch over large areas of the Caribbean. These clumps of seaweed can make landfall and lead to large mats of material piling up very quickly over long stretches of beach. Once on land, the seaweed decays and exudes a distinct rotting smell which can be detrimental to tourism and quality of life in the area. The observed mass of Sargassum seaweed has grown noticeably since 2011 and doesn’t seem to be slowing down. The Sargassum has many oxygen-filled pneumatocysts, so it floats on the ocean surface over large areas. Given this information, we assume the Sargassum’s dynamics will be closely related to that of the surface currents themselves. Surface current data from High Frequency Radar (HFR) measurements along the south coast of Puerto Rico were used to produce animations of surface drift which revealed the general flow in the region. The surface current measurements were compared against the US Navy’s AMSEAS model to assess the model’s ability to estimate the flow in the region. Within this research program it was assumed that the velocity of the Sargassum should be similar to the surface currents. The HFR and model animations were examined over hourly, daily, and monthly time intervals. The ocean model captures the direction of transport well but appears to consistently predict faster currents than those measured by the HFR. The model estimates and the HFR measurements agree much of the time, however, there are some time periods where the model would not help with the tracking of the floating particles. This research revealed that the movement of the surface particles are typically westward, close to the southern shore of Puerto Rico during most of the time periods covered in our study. Sometimes a rapid change in this behavior was observed, where surface particles moved directly towards the southern shore of Puerto Rico, or toward the east. This information could possibly be made available for ecological and economic use by stakeholders and businesses on coastal tourism locations, as well as search-and-rescue use by Coast Guard or similar institutions.