Severe Surges of Sargassum Possible Across T&T’s Shores Through May

Decaying Sargassum at Guayamare Beach, Toco on March 20th, 2021.

Moderate to severe surges of Sargassum are forecast to impact the Lesser Antilles over the next coming months. This is according to the latest Sargassum Sub-Regional Outlook Bulletin published by the UWI Centre for Resource Management and Environment Studies (CERMES), Cave Hill, Barbados.

During the first quarter of 2021, Eastern Caribbean Islands saw moderate to severe influxes of seaweed, but the level that is arriving now has increased considerably. According to the report, there is 6% more Sargassum visible in the Atlantic than there was this time last year. Still, it is below 2018 levels, which were the worst recorded to date.

A Portuguese Man o' war Jellyfish entangled in Sargassum seaweed, seen on April 4th, 2021 on Indian Bay, Mayaro. Thick, decaying yellow-green Sargassum lay on the sands of Mayaro beach, with the pink to purple jellyfish in the center of the image.
Portuguese Man o’ war Jellyfish entangled in Sargassum seaweed, seen on April 4th, 2021 at Indian Bay, Mayaro.(Rushton Paray)

At least through May 2021, islands across the Eastern Caribbean are set to receive moderate Sargassum influxes, with severe surges, particularly for the Lesser Antilles’ southern islands.

Northern islands are set to receive moderate influxes from late March to April, with little to nothing in May. Middle islands will continue to experience moderate influxes over the next three months, similar to last year without the major peak seen in May. After a light two months, the southern islands are expected to receive severe sargassum influx in peaks over the next three months. For Trinidad and Tobago, the spike in seaweed mats begun in March and is forecast to continue through May.

A map of the Lesser Antilles on the left, with graphs showing the abundance of Sargassum, as detected by satellite images, on the right. Northern islands, from Dominica northward, are set to receive moderate influxes from late March to April, with little to nothing in May. Middle islands, from Martinique to St, Vincent, including Barbados, will continue to experience moderate influxes over the next three months, similar to last year without the major peak seen in May. After a light two months, the southern islands, from the Grenadines to Trinidad and Tobago, are expected to receive severe sargassum influx in peaks over the next three months. For Trinidad and Tobago, the spike in seaweed mats begun in March and is forecast to continue through May.
The prediction graph below illustrates a comparison of 3+ month forecasts using a relative index of Sargassum from processed satellite images by SaWS (USF/MODIS+) and SAMtool (CLS/Sentinel+). Close overlap of the two lines on any one graph indicates that the predictions are similar between the two datasets. (CERMES)

The outlook notes stakeholders in the tourism industry can expect more-or-less continuous mild to moderate influxes over the next few months in the middle and northern islands. However, the tourism industry in the southern islands, including T&T, could be hard hit with continued mass influxes.

Fisheries will also be impacted, as traditional pelagic fishing season got off to an unexpectedly slow start given the absence of Sargassum.

Beaches and shore-side markets will likely require significant cleanup efforts to prevent problems with trapped sargassum rotting.

Offshore vessels particularly in the southern area should be cautious when traveling at night to avoid becoming trapped in large sargassum mats

Sargassum inundation risk as of March 15th, 2021 (left) and March 29th, 2021 (right) classifying the risk into three categories: low (blue), medium (orange), and high (red). National Oceanic and Atmospheric Administration (NOAA), and the University of South Florida (USF)

As of March 29th, a report by the National Oceanic and Atmospheric Administration (NOAA) and the University of South Florida (USF) show varying levels of risk for Sargassum landings across T&T. Across much of Trinidad, the risk level is low, except an area between Mayaro and Manzanilla, where the risk is high. Across Tobago, the western half of the island is at low risk, while the eastern half of the island is at moderate risk, joining coastlines across Grenada northward, where moderate to high risk is forecast. Barbados and the French Antilles are under a high risk of Sargassum landings through the next several weeks, particularly Atlantic-facing coastlines.

Officials in Tobago already notice a proliferation of Sargassum on the island’s coastlines. Richard Hinds, a coastal engineer, attached to the Division of Infrastructure, Quarries and the Environment in Tobago state, there are two approved sites across Tobago to deal with Sargassum’s burial in Delaford and Friendship Estate. He notes these sites are away from the public.

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