Sargassum – good or bad?


Andrea Kay

Written by Andrea Kay Intern with Pinelands Creative Workshop in Barbados
Under graduate Studies – York University, Canada
Bachelors in Environmental Studies, with Specialized Honors in Environmental Politics




What is Sargassum Seaweed?

Sargassum seaweed is a brown, free-floating algae that originates from the Sargasso sea. The Sargasso Sea, which exists exclusively in the Atlantic Ocean (specifically, in the North Atlantic Gyre), spreads approximately 2 million square miles. This sea is the only sea without fixed land boundaries; dynamic ocean currents form its limits (which are solely created by the North Atlantic Gyre). The species of Sargassum found here are ‘holopelagi‘ – meaning they float and reproduce at high seas (not on the ocean floor). A distinguishing feature of this sea is its really clear blue water – divers would be greeted by 200 feet of visibility.

sargassumThe North Atlantic Gyre is what helps move the seaweed worldwide within the Atlantic Ocean, affecting multiple continents and countries. The North Atlantic Gyre is one of the five major oceanic gyres. It is a circular system of ocean currents that stretches across the North Atlantic from near the equator almost to Iceland, and from the east coast of North America to the west coasts of Europe and Africa. The currents that compose the North Atlantic Gyre include the Gulf Stream in the west, the North Atlantic Current in the north, the Canary Current in the east, and the Atlantic North Equatorial Current in the south. The Gulf Stream in the West is what carries the seaweed to the coasts of Barbados.

What affects the changes in the Gulf Stream?

Affecting the Gulf Stream is the occurrence of El Nina or El Nino. El Nino and El Nina concentrate action within the Gulf Stream by the strong winds and surface wave action. As different years bring different surface water movements
and wind patterns, this can change where the Sargassum seaweed goes and to what concentration it accumulates in. As of 2015, we are currently experiencing El Nino weather patterns, meaning unusually warm temperatures in the Pacific. This can also affect global temperatures and rainfall. Online articles report that El Nino is only strengthening as the months pass, meaning these weather increases are likely to last through the fall and the end of the year. This ultimately means a large abundance of seaweed may be semi-permanent throughout the year within Barbados.

Why is Sargassum Seaweed in such a high abundance?

Nutrient-rich coastal water breaks away and drift into the Sargasso Sea, supporting the algal growth. The over development of the Sargassum seaweed as experienced in Barbados, is due to a nutrient overload. The nutrients in question are Nitrogen and Phosphorus. Although these elements are needed for healthy life in small quantities and provide sufficient nutrients for life to flourish, an overload of such nutrients can cause life to disintegrate. As seen with the unusual abundance of Sargassum, Nitrogen and Phosphorus overload can cause too much algae growth, which will blanket surface waters causing the algae to absorb most to all of the sun’s nutrients, whilst darkening the water below it. When this happens, especially in coral dominated water, pelagic (surface water) fish and coral become deprived of the sun’s nutrients, and can cause a lack of photosynthesis among coral reefs and other marine plants. Along with this, the nitrogen and phosphorus rich algae absorb most of the oxygen out of the water, creating an overload of carbon dioxide to sit within the ocean. The over-abundance of carbon dioxide suffocates any wild life within the water, causing death amongst many fish. Without a balance of oxygen within the water, the oceans PH levels are also at a higher acid content than what is naturally intended. The higher acidity levels will not directly harm humans, but will affect any shellfish. Shellfish all have a calcium base within their hard exterior shells, when the water becomes too acidic, it dissolves these hard shells, leaving many species unable to defend themselves and ultimately, live.

A map shows sea surface temperatures on July 28, 2015

A map shows sea surface temperatures on July 28, 2015.

The abundance of Sargassum creates issues within the major industries like Tourism and Fisheries, due to its invasiveness on the shore and in the water. Clogging boat engines and propellers, killing multiple fish species that are used for eating and encouraging the flourishing of invasive species like the Lionfish, are few examples of Sargassum-related issues within the sea. On land, the seaweed poses a mild threat to human health and sanitation with tourists and locals. When decomposing, a foul, rotting odor is given off of the seaweed, driving all tourists away from the beaches, which is a place of business for many locals. Even when tourists linger on the beaches, the odor tolerated is hydrogen sulfide. This is deemed a poisonous gas, especially during the peak summer months due to the high heat, humidity and abundance of seaweed accumulated. Inhaling the gas in small doses could trigger irritation of the eyes and the respiratory system, especially among people who have mental sensitivities. The groups at risk are people with respiratory problems, asthma patients, elderly people, babies and pregnant women. Certain animals, especially dogs, are also sensitive to the inhalation of Hydrogen Sulphide. There is also sea lice living inside the seaweed; when touching the seaweed, the lice are able to bite and irritate the skin, leaving the victim itchy, with red bumps all over the body. Although these effects don’t last long, people with skin sensitivities may be more at risk of serious, long-lasting effects.

Is there any benefits to Saragassum seaweed?

Sargassum seaweed, in moderation, is beneficial for the sea, providing a rich source of nutrients and habitat/protection for many creatures that dwell within the ocean. In fact, several creatures, like the Sargassum fish (a type of frogfish), are born, reproduce, and die solely within this environment. Many fish eaten off the coast of Barbados especially, like mahi mahi (a.k.a. dorado, dolphin), sailfish, jacks and amberjacks use this seaweed as a nursery habitat for their offspring.

What are the contributing variables to the high abundance of seaweed?

From 4 to 5 years ago, massive amounts of Sargassum fouled beaches in Florida, Africa, Bermuda, and the eastern Caribbean region in which the unusual abundance of this seaweed was noticed amongst tourists and locals. The unusual high abundance of seaweed is no accident, for many factors are contributing to the invasive amount that is currently still affecting many coastal zones around the world. One contributing factor is due to the BP oil spill that occurred in 2010 on the Gulf of Mexico. The sheer amount of oil that spilled into the ocean needed large measures to absorb and pick up the multitude of oil slicked on the surface. One method was using nitrogen and phosphorous-based dispersants to ‘break’ up the oil. Obviously, using this product created an overly high abundance of nutrients to be within the water chemistry. On top of this, climate change has been contributing to the intensive growth of the seaweed. The warming of the earth and the raising of average climate levels has made it easier for things to flourish: mosquitos, diseases and Sargassum seaweed.

Where is the seaweed primarily drawn from?

Although it occurs in South Africa, there is a common misconception of the African Continent being the main distributor and creator of the Sargassum seaweed, which is strictly not true. As many parts of the world are shared with the Atlantic Ocean the seaweed is drawn from many places globally (this year, Professor Hazel Oxenford explained that research now showed that the seaweed was coming from a new source in the Amazon, and was also being reported in Venezuela and Colombia).



Posted in