In the early fifteenth century, Portuguese sailors reached a becalmed part of the Atlantic Ocean, coated with mats of gold-brown seaweed. Under windless skies, their ships drifted idly with the currents. The sailors named the seaweed Sargassum — after its resemblance to a Portuguese plant — and the region eventually became known as the Sargasso Sea.
Initially thought to be an oceanic desert, this part of the Atlantic is now recognized as a watery rainforest. It is one of Earth’s most rare and valuable marine ecosystems, so rich in nutrients that eels travel thousands of kilometres from rivers in Europe and the Americas to breed there.
The Sargasso Sea is a clockwise circulating gyre that encompasses nearly two-thirds of the North Atlantic Ocean, unique in being the world's only sea that does not have a coastline; circulating ocean currents accumulate “floating reefs” of brown Sargassum seaweed to create its only border. You'll also find here free-floating brown macroalgae (phaeophyta) - the golden rainforest of the sea. The Sargasso Sea is home to several iconic species including the Bluefin tuna, eels, sea turtles, the endangered Bermuda Petrel (seabird) and the critically endangered Porbeagle shark which is threatened by overfishing and the North Atlantic “garbage patch” of consolidated plastic waste.
But the Sargasso Sea is also one of the dirtiest and most damaged parts of the open ocean. The gyre of currents that bounds this shoreless sea entraps vast amounts of plastic waste, and fish stocks are declining in the now-busy shipping route.