For tourists visiting beach resorts around the Caribbean, who expect to see the sublime, pristine beaches depicted on websites, are instead shocked to find beaches littered with piles of decaying seagrass, smelling of rotten eggs. Especially after a storm with strong on-shore winds it is not uncommon to find your beach covered with Sargassum seaweed.
Welcome to the Sargasso Seaweed Experience
Unless you are a mariner you might have never heard of the Sargasso Sea, that giant mat of algae floating off the Bahama Islands eastward for hundreds of miles, toward the Azores.
Ancient mariners from the Phoenicians to the colonizers of North America, were intimately aware of the Sargasso Sea because it lay astride the ocean currents that carried their vessels from Europe and North Africa, westward toward the Caribbean. Ship’s logs would record a mass of sea grass sometimes so thick as to capture their vessels in an impenetrable embrace. What it was and where it came from remained a mystery for centuries. (map – NOAA)
By the 20th century scientists had unraveled some of the mystery. They discovered that the algae originated in the Gulf of Mexico and Caribbean and was carried by Gulf Stream currents into the warm waters of the Atlantic south of Bermuda. There the algae bloomed, fed by nutrient rich waters, like the agricultural runoff from the Mississippi River of North America.
An ecosystem rich in biodiversity
Researchers also discovered that the Sargassum algae supported a unique ecosystem, rich in biodiversity including numerous species of fish, sea birds and turtles. However, there are recent indications that even though the Sargasso continues to grow in size, its marine biodiversity is diminishing. And that could be a signal that something is seriously out of balance. (video – MBARI)
In 2014 reports were appearing of massive mats of seaweed 3-4 feet thick, collecting on beaches around the Caribbean. By August of 2015 the reports were describing mats 10 feet thick washing ashore. The alarming news indicated what seemed to be a massive algae bloom that could threaten the tourism industry throughout the Caribbean and Gulf of Mexico. Beach resorts were not alone in being threatened, marine life was also in jeopardy. Sea turtles could not nest on beaches or hatchlings reach the sea through tangled masses of seaweed.
Out at sea the floating mats were so dense as to cut off light and oxygen creating dead zones of decaying matter with high levels of hydrogen sulfide and bacteria.
What are the causes of this explosive Bloom?
The warmer sea temperatures that are necessary for the bloom are a clear result of global climate change. This combined with increased levels of nutrient, not from the Gulf of Mexico but from Brazil, where deforestation and industrialized farming along the Amazon River have raised nutrient levels flooding into the Atlantic.
A final element plays into this perfect storm. There is evidence that the Gulf Stream which would normally carry sargassum farther into the Atlantic is slowing. These factors have combined to generate the massive algae bloom, suffocating beaches throughout the region and costing the tourism industry hundreds of millions to clean up the mess. (photo – Alonso Cupul)
As Sir Hilary Beckles of the University of the West Indies said recently: “Herein is an endemic and systemic threat to the resilience and development of these nations and therefore we must have an international response to this… We must show our children enjoying our beaches and give visitors the assurance that the weed is not killing us and that life goes on. We must let people know that we in the Caribbean are not sitting on our hands but trying to find solutions to the threat presented by the Sargassum weed.”
By Robert Frerck, Blue Ocean Network
Find out more about the Sargasso Sea here: