Sargassum in the Sargasso Deep Blue

Coastal geology & environment, Environmental, Geography, Natural Environment

Anyone who has heard anything about the Sargasso Sea will have probably learned that it is unique among the planet’s seas in that it is completely bereft of any land boundaries and that it is full of seaweed. The boundaries of the sea are the four directional currents (N-S-E-W) which together create a clockwise-circulating system of ocean currents known as the North Atlantic Subtropical Gyre. This novel geographical oddity results in a clear, deep blue sea which is relatively warm and calm compared to the rest of the cold and often turbulent North Atlantic.

Sargasso Sea (old Dutch map)

The Sargossa’s seaweed is planktonic (ie, floating freely), a genus of seaweed called Sargassum—hence the source of the sea’s name which is thought to be of Portuguese origin (also cf. Sp. sargazzo (“kelp”)—a golden-brown-coloured algae which reproduces vegetatively on the surface and never attaches itself to the sea-bed floor during its lifecycles, which marks it out from the typical behaviour of seaweed on the high seas. The sargassum forms itself into concentrated patchesA⃣ which drift around the sea’s circumference while being ecologically beneficial to the local marine life – providing a habitat, sanctuary and food for turtles, shrimp, fish, porbeagle sharks, eels and the like.

image: National Ocean Service

Sargassum on steroids The Sargasso and its seaweed (more correctly gulfweed) has been much in the news recently due to increasing amounts of it washing up on the shores of beaches in eastern Mexico, Florida and the Caribbean, causing a nuisance to sunbathers, coastal dwellers and even a potential hazard, and happening earlier in the calendar year than in previous yearsB⃣. Marine scientists attribute the recent explosion of gulfweed (the Great Atlantic Sargassum Belt) to human activities such as intensive soya farming in the Congo, the Amazon and the Mississippi, which dumps nitrogen and phosphorus into the ocean (Barberton 2023).

A carpet of pelagic sargassum covering the beach on the Barbados east coast (photo: H Oxenford)

Sargasso lore The Columbus expedition on route to the East Indies (or so he thought) in 1492 gave us the first recorded sighting of the seaC⃣and navigators and sailors have been long been wary of the suspected dangers thought lurking in the mysterious sea…in fear of their vessel being permanently entrapped in its becalmed, windless waters (known as “the Doldrums”) or inextricably entangled in the ubiquitous brown belts of seaweed. Columbus and later navigators sought to transit through the sea by manoeuvring around the masses of seaweed, fearful as Columbus was that the algae mats concealed coral reefs that would wreck their ships.

Christopher Columbus (source: hoidla.spordimuuseum.ee/)

Eco-hazards: the North Atlantic garbage patch While the imagined threats to sailors and ships have not materialised over time, the real threats, aside from the runaway sargassum blooms, are those that are posed against the long-term health of the sea itself. Passing shipping has had a negative impact on the ecosystem of the Sargasso Sea. Storms and hurricanes transporting massive amounts of human-made pollution, followed by the characteristic stillness of the Sea, has made it susceptible to large-scale garbage accumulation, especially of microplastics (with volumes increasing exponentially the danger of increased plastic ingestion by marine life is a major concern). Other threats to the Sargasso come from climate change and overfishing of its waters. The future harvesting of sargassum seaweed is also a concern for marine biologists.

Sargassum floating on the Sargasso Sea (photo: David Doubilet/National Geographic)

Endnote: Bermuda Triangle intervention in the Sargasso circle? While the Sargasso Sea has no land borders, there is land in the form of the tiny Bermuda islands on the Sea’s western fringe. The intriguing nature of the Sea is further accentuated by association with Bermuda, or more specifically with its Bermuda Triangle reputation – a series of legends and mysteries that have grown up over the last century about a supposed abnormal pattern of aircrafts and ships disappearing without trace in the loosely-defined “Triangle” areaD⃣.

source: Shutterstock

Dimensions: the Sargasso Sea is elliptical in shape and encompasses an area of >1,000 mi in width and 3,000 mi in length; the Bermuda Triangle (aka Devil’s Triangle) is roughly 500,000 sq mi of water in a space bounded by Florida, Puerto Rico and Bermuda.

source: bibliotecapleyades.net

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A⃣ a “golden floating rainforest” (Dr Sylvia Earle)

B⃣ and not confined to the eastern side of the ocean, the media has reported the presence of giant sargassum blooms from West Africa right across to the Gulf of Mexico (‘The Aussie tackling an ocean-spanning seaweed monster’, Angus Dalton, Sydney Morning Herald, 26-April-2023, www.smh.com.au)

C⃣ though 4th century AD Roman writer Avienius referenced an ancient Carthaginian exploration of it that supposedly took place, and there were claims on behalf of Arab mariners from the 11th and 12th centuries

D⃣ critics have generally debunked the idea of the Bermuda Triangle as a nemesis, arguing that there is no evidence that mysterious disappearances occur more frequently there than on other well-frequented oceanic transit route, that the “phenomena” is a manufactured one, sustained by conspiracy theorists and media sensationalism

𓆝 𓆟 𓆞 𓆝 𓆟

Articles and other publications consulted

‘About the Sargasso Sea’, Sargasso Sea Commission, www.sargassoseacommission.org/

‘Maritime Heritage’, Sargasso Sea Commission, www.sargassoseacommission.org/

‘What is the Sargasso Sea?’, National Ocean Service, www.oceanservice.noaa.gov/

‘The Aussie tackling an ocean-spanning seaweed monster’, Angus Dalton, Sydney Morning Herald, 26-April-2023, www.smh.com.au/

‘The creeping threat of the Great Atlantic Sargassum Belt’, Zan Barberton, The Guardian, 07-Mar-2023, www.theguardian.org/