Sargassum solution still unsolved

Hurricanes used to be the main natural phenomenon in the Caribbean feared by residents at this time of year but sargassum is becoming a problem that is causing immense damage ecologically and financially.

The Cayman Islands has suffered the effects of sargassum in recent years and throughout the region entrepreneurs, scientists and biologists are trying to figure out how to tackle the smelly, rotting seaweed which is impacting the already badly hit tourism and fishing industries. Some of Jamaica’s finest beaches – particularly Hellshire Beach - are affected by it, as a most countries in the region.

For the past 11 years, the Caribbean has experienced masses of the floating brown algae that often end up inundating beaches. Although small quantities usually begin arriving from March, the large influxes usually start in May and end in November.

2018 was an exceptional year when there was a record 20 million metric tons of sargassum throughout the Caribbean.

Sargassum seaweed has been called “the golden floating rainforest of the sea” because it is inhabited by numerous marine animals, some of which are found nowhere else. Many other species feed and hide from predators under the mats of floating seaweed. Fishers even report that they are able to catch large fish when the sargassum is in the sea. However, when the massive blooms wash up on to beaches and into shallow near-shore waters, it causes grave problems.

Sargassum seaweed, if left in huge piles on a beach or in the water near the beach begins to rot. The rotting weed also produces hydrogen sulphide, a toxic gas that smells like rotten eggs. The rotting seaweed also stains the seawater brown. Fish and invertebrates in the water die due to low oxygen and the presence of the hydrogen sulphide.

Sargassum also helps to erode beaches as the waves that pound the shore are made heavier by the floating sargassum thus removing sand, which is washed offshore. In addition to making the beach unpleasant and unusable, and killing especially small fish, fishers report entangling of their nets and engines by the seaweed mats resulting in engines overheating and nets becoming full of seaweed, rather than fish, causing them to spend hours cleaning their gear.

Since the start of the sargassum invasion, many uses have been identified, and scientists from Barbados have produced a 172-page Sargassum Uses Guide. The guide documents sargassum use in construction - to make bricks - and to manufacture fertiliser and bio-stimulants, in biogas production, pharmaceuticals and cosmetics, to make bioplastics, paper, plant-based leather and rubber, in water purification, to make lubricants, and in environmental restoration. Companies like Algas Organics, based in St Lucia, and others have established factories that produce fertiliser from sargassum. Sargassum naturally contains high levels of arsenic, but these companies have developed technology to remove the arsenic so that their product is safe for use on food crops. However, use of the unprocessed sargassum can transfer unacceptable levels of arsenic to foods. 

The increase in sargassum is connected to climate change, increase in chemical and toxic waste in seas. In the meantime, unfortunately, the sargassum conundrum looks likely to increase.