Caribbean: Tracking Sargassum Seaweed ‘Invasions’ via Satellite

Since 2011, massive quantities of floating sargassum seaweed, also known as sargasso, has floated throughout the Caribbean, impacting marine resources, fisheries, shorelines, waterways, and tourism. The amount of observable weed has lessened since the largest bloom of October 2015; however this process is cyclical and the coming 2017-2018 season is projected to see a significant increase of this ocean-carried weed. Local governments are finding new ways of tracking the weeds, including looking to space.

Published 6 years ago, updated 4 years ago

This article was published in Caribbean Compass in September 2017.

The actual sargassum route and cycle are not well known, but volume does seem to be increasing with each season’s cycle; theories for this include increased heat and/or additional nutrients introduced into the Atlantic that creates or enhance massive blooms of this foliage. Recent research also suggests that Atlantic algae respond positively to increased C02 and acidity in seawater, a major change in the former theory of slower growth.

In cases where sargassum accumulates and decomposes in large quantities, the smell of rotten eggs can occur. This is the odor of hydrogen sulfide gas, which is given off as part of natural decomposition. The US Occupational Safety and Health Administration notes that when the smell is described as “more offensive” (three to five parts per million), prolonged exposure might cause effects such as nausea, tearing of the eyes, headaches, and loss of sleep. Asthma sufferers may experience airway problems. Full details from the OSHA report can be found here.

Sargassum also effects fishing gear and motors, and some fishers and other boaters are coming up with devices to free rudders of weed and to deflect sargassum from propellers. They are using strainers across the water intakes to prevent blockage and engine overheating. Those navigating through the islands need to be prepared to deal with gear complications plus possible loss of power or steering, and plan for the safety implications of this, especially when underway at night.

Wildlife has also been affected. Heavy mats of sargassum along the shoreline, such as occurred on the east coast of Barbados in 2015, can prevent hatchling sea turtles from reaching the water.

Being proactive and keeping informed about the location of these floating mats of seaweed will be the new reality for those in the Caribbean — islanders and sailors alike. Some Caribbean island governments, such as Tobago, are already looking at satellite tracking to help cope with sargassum inundations.

Satellites Spot Sargassum

Over the past several years, several research facilities have been developing technologies based on satellite imagery to identify the location of weed masses. While this seems straightforward – just look down from the sky! – it has required on-the-ground, or in this case sea, knowledge of where volumes of weed occur. This then allows comparison to satellite data to develop suitable applications.

For several years, citizen scientists and cruisers have reported their sargassum findings to the Gulf Coast Research Laboratory’s (GCRL) sargassum research group headed by Jim Franks of the University of Mississippi. This data is used to model the movements of sargassum in the tropical North Atlantic and Caribbean. This information has also been used to determine the point of origin of the massive blooms. GCRL research indicates an equatorial origin, rather than a connection to the Sargasso Sea – the middle of the North Atlantic Gyre.

The GCRL research conducted by Franks and oceanographer colleague Dr Don Johnson is ongoing. Another effort to provide a satellite tracking application was being developed by Dr Chuanmin Hu’s group at the University of South Florida. There is now a website with satellite imagery views of sargassum, which may provide early warning of where or when seaweed will arrive in an area. While still in the development stages, this is a huge step forward for projecting where the weed will be and could allow countries in the impact areas time to prepare.

Thanks to this information, along with the work of Jim Franks, the paths and patterns of sargassum weed are becoming better known; ongoing research will allow a better understanding of variation and aggregation patterns. According to Dr Hu, “…if there is a large sargassum aggregation in a ‘hotspot’ in the Atlantic in February, we can predict that there would be major blooms in the Eastern Caribbean in spring and summer. So this prediction gives at least two months of lead-time to respond to beaching events. For example, back in February this year we predicted that this will be another sargassum year for the Caribbean, and this turned out to be true. Longer-term prediction (e.g. next year or future years) is currently not possible because we don’t know what caused inter-annual variations in the past, although in general, we believe that future years more or less will also have similar events.”

How Can Cruisers Help?

Cruisers can help by spreading the word to other concerned people and continue to report when and where you see the weed. This is especially important as now there is a working prototype for the early warning system. More testing and visual confirmations for predictions are critical. More data points mean more accurate prediction models, and there are still other parts of the tropical Atlantic to be added. This is especially critical for the equatorial cruising regions from West Africa to South America and the Caribbean, where transatlantic sailors, such as those in the Atlantic Rally for Cruisers (ARC), can face serious impacts. (Solo sailor Donna Lange, during her 2015-2016 circumnavigation, was trapped in sargassum weed off Africa; she had to use a machete to cut her boat free from a vast solid mat of weed more than a foot deep.)

By reporting data, cruisers will allow Dr Hu’s team to fine-tune the processing tools. GCRL’s Senior Scientist, Jim Franks, asks cruisers to input their observations and data including latitude and longitude, photographs if possible (Jim will provide contact information in direct response to a report), and comments, to a website designed for reporting pelagic sargassum observations in the Caribbean and tropical North Atlantic. Data provided to this site will continue to be used by GCRL scientists and colleagues throughout the region to identify the source and examine the movements and causes of extraordinary sargassum events.

Contributions to the project can be made at the GCRL website. Likewise, and the Sargasso Sea Commission have also developed a reporting system where detailed information can be submitted through a reporting card and e-mailed to PhD student Mengqiu Wang, who is looking for validation of satellite observations. In support of this data collection effort, the international Seven Seas Cruising Association — the world’s largest association of cruising sailors — is actively notifying their network of members via website and publications. We suggest other organizations do the same.

Satellite-based Sargassum Watch System (SaWS), 

The Sargassum Watch System (SaWS) is designed to use satellite data and numerical models to detect and track pelagic Sargassum in near-real time. Find out more about the spread of this seaweed throughout the Atlantic, Caribbean Sea and the Gulf of Mexico and how it might affect your cruising choices.

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