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    August 12

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SARGASSUM: Friend or foe?


Added 16 August 2019


Sargassum seaweed washed up on a beach. (Picture courtesy Sustainable Caribbean)

In 2011, two species of the brown, salt water macroalgae scientifically referred to as Sargassum natans and Sargassum fluitans floated their way into the Caribbean Sea and have returned almost annually since.

The Sargassum seaweed is one which is never attached to the sea floor but floats on the surface of the water due to special air sacs. It is not to be confused with the sea moss used in the popular drink - if it was, then we would have definitely struck Bajan Gold! 

Each year, the Caribbean islands as well as the West African coast have been experiencing influxes of the seaweed. It is believed that the new source region (which is not the Sargasso Sea) is encircled by currents running clockwise from South America to Africa and back again.

During certain parts of the year, it appears as though that loop breaks down and sweeps sargassum up the Brazilian coast toward the Caribbean, blooming and growing as it moves. Recent research has indicated that the massive algal blooms occur in the equatorial area of the Atlantic known as the North Equatorial Recirculation Region (NERR).

It is thought that a combination of factors such as nutrient inputs from the Amazon River and Congo River,  changes in ocean chemistry and currents, increased sea surface temperatures and increased iron deposition from airborne Saharan dust could be causing the increase in growth. 











Threat or Goldmine?

Sargassum has shown to be beneficial in small amounts but has posed massive challenges in large amounts. While floating at sea,  pelagic sargassum seaweed plays an important ecological role. Many small, invertebrate animals and even other algae are associated to sargassum, which may be a potential transport vector for exotic species. There has been an increase in landings of dolphinfish (but mostly juveniles) and amber fish.

However, fish landings have mostly declined, while coral reefs and associated ecosystems, and sea turtle nesting beaches are degraded by the decaying seaweed or clean-up operations. If a small amount washes up on the beaches, it can be beneficial to the wildlife such as seabirds acting as an additional source of food and can also contribute to beach nourishment. 

However, after one’s first experience with sargassum, many would consider it to be a nuisance. This is mainly due to the unpleasant sight and smell. Locals and visitors have been used to the white, sandy beaches and crystal clear seas and now have to adjust to the ‘Brown Invader’. In recent years, islands reported a drop in tourist arrivals during the periods of influx with some vacation cancellations, putting a strain on the regional tourism industry.  

The sargassum seaweed has also impacted the fishing industry by damaging fishing gear and equipment, blocking water intakes and tangling up in nets and lines as well as making it difficult for some boats to go out fishing. 

How Can We Use It?

So now that it seems here to stay, how can we use this resource?  Some entrepreneurs and innovators have started to do research and development and have created products out of the sargassum. For example in Barbados, some of these products include as a biostimulant by Red Diamond Compost, as an ingredient in soaps by Oasis Laboratory and also being used as a growing substrate for beetroot (Design Council) and other crops. 

There is still a need for greater investment from both private and public sector to assist research in order to determine the economic potential of sargassum as well as potential negative human impacts due to high levels of arsenic and the potential implications when added to soil. With increased investments into innovation, we can turn this problem into profit.

Within the region, the Centre for Resource Management and Environmental Studies (CERMES) at the University of the West Indies, Cave Hill has been leading the way when it comes to research. Most recently, the application of drone technology has been used to determine the quantity of sargassum on the beach on the East Coast of Barbados. 

The Sargassum seaweed is a natural phenomenon and so ideally, nature should be left to run its course. In extreme cases, seaweed can be cleared off the beaches preferably without the use of heavy machinery and equipment that can lead to beach erosion and disrupt habitat. Therefore, manual cleaning up of seaweed is preferred but it is imperative to check for wildlife before.

In addition, it is important to recognise that seaweed will also trap litter. The plastic materials which become trapped have a high chance of washing into the ocean and affecting the ecosystems. As a precaution, be mindful of what you leave on the beaches and pick up any garbage regardless of who it belongs to. 

Written by Georgina Archer, Sustainable Caribbean intern and Nikola Simpson with contribution from Shelly-Ann Cox and Hazel Oxenford. 

To learn more and read an extended blog on the topic, visit https://www.sustainable-caribbean.com or email info@sustainable-caribbean.com


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