There are few places on Earth that remain as shrouded in mystery as the Bermuda Triangle.

Although the National Oceanic and Atmospheric Administration does not recognize the spot in the Atlantic Ocean as a real place, legend has it that Miami, Florida; San Juan, Puerto Rico; and the island of Bermuda form the points of a surprisingly treacherous stretch of water. Depending on how you look at it.

This 1,300,000 to 3,900,000 square kilometers of ocean is said to be the site of dozens of unexplained ship and plane disappearances blamed on everything from the likes of alien abductions to interdimensional voids sucking in unsuspecting sailors. While these fanciful theories are unsubstantiated, the fear and mystery surrounding this patch of ocean must have come from somewhere. And it may be wrapped up in the ensnaring seaweeds that overrun the waters of the Bermuda Triangle.

In fact, there is a ton of seaweed in a very real area of the Atlantic Ocean that the Bermuda Triangle overlaps with, called the Sargasso Sea. [Intro music] The Sargasso Sea takes its name from its most enduring and iconic inhabitant: a type of free floating, yellow seaweed called Sargassum. The sargassum is kind of corralled in the sea by five constantly circling currents. Because the Sargasso Sea is the only sea without a land border!

Instead, it sits in the center of those currents, still and calm like the eye of a hurricane. So this floating, golden rainforest can be a peaceful haven of biodiversity, providing an essential habitat, breeding ground, and food source for marine life from shrimp to sharks But, at the same time, the dense, thick mats that make it a perfect habitat for aquatic wildlife can also make it a sailor’s worst nightmare: a deadly trap for small boats. The seaweed meadow has been a source of fear to sailors for hundreds of years.

In the 1400s, Spanish sailors feared that the presence of Sargassum meant they were in shallow waters, and would soon crash into the shore. But what they didn’t know is that the floating sargassum found in the Sargasso sea is unique among seaweed because it begins its life a nd reproduces on the high seas, unlike other seaweed which does so on the seafloor. This allows its great golden tides to travel far and wide, Did we mean for it to rhyme? recreating the dense seaweed forest of the Bermuda Triangle in new places.

And since the 1970s, Sargassum has been doing just that, reaching its ensnaring yellow tendrils farther than ever with unprecedented growth, spreading across the Atlantic to create more deceptively deadly traps. And in 2011, something new happened. A monstrous mass of Sargassum made its way across the Atlantic all the way to the coasts of West Africa where currents caused dense golden mats to wash up on beaches across the African coastline.

This great seaweed blanket was anything but comforting. It blocked fishing nets and prevented small fishing boats from traversing shallow waters, causing food shortages in small villages that depended on fish. 2011 might have been the first year this bloom was reported, but it’s reoccurred every year since. And researchers think the major shift might have happened thanks to us.

Sargassum mega-blooms feed on human sewage and agricultural run-off from rivers that flow into the ocean. Like in the Gulf of Mexico, where lots of Sargassum grows, 80% of the freshwater comes from the Mississippi and Atchafalaya rivers. And these rivers deliver a veritable feast of nutrients like nitrogen and phosphorus to Sargassum.

So you end up with eutrophication: when aquatic plants gobble up excess nutrients in the water to grow. But human activity is making the situation much worse. Synthetic fertilizers and sewage from urban areas add tons of nitrogen to our rivers.

Literally. Synthetic fertilizers alone add 121 million tonnes of nitrogen into the ocean every year. And the use of synthetic fertilizers has ramped up by 800% since the 1960s.

So it’s no surprise that we’ve seen nitrogen levels in Sargassum increase in that time as well. Granted, not by 800%. But a 35% rise in Sargassum’s nitrogen content is a pretty big jump in its own right.

All that extra input from the land lets Sargassum grow unchecked by normal nutrient limitations, with satellite images showing an estimated one million tonnes of the seaweed traveling from the Gulf of Mexico to the Atlantic each year. But agriculture is not the only culprit here. Researchers also suspect that deforestation of the Amazon is playing a role in the seaweed swarm.

Losing huge swathes of trees may increase the amount of nitrogen and phosphorus in the soil, which is quickly washed into the Amazon river by heavy rainfall. Add a global climate crisis on top of that and we get more extreme flooding of the river since the 1990s, washing even more nutrients into the water. Then, because Sargassum can float untethered through the ocean, it can be carried by currents to colonize the best, most nutrient rich waters and expand into a dense web of golden tendrils which strikes fear into sailors hearts.

But, while the Sargassum travels over the ocean to Africa, a portion of the nutrients that fed it in the first place might have traveled by air from there. Researchers suspect that east to west blowing winds carry smoke from burning vegetation in central and southern Africa across the Atlantic, delivering a rich source of nitrogen, phosphorus, and iron to waiting Sargassum. So Sargassum is growing and traveling more than it used to.

And, as you might expect, the Bermuda Triangle coming ashore brings its own unique set of issues. The tangled mess of Sargassum building up along beaches and in the water can trap sea turtle hatchlings and prevent them from reaching the sea. I know how much everyone loves the baby sea turtles, but there’s more.

This ever expanding seaweed mass also sucks up all the oxygen from the water it inhabits, leaving massive dead zones where other marine life can no longer survive. So maybe there’s a reason people have feared the ensnaring powers of the Bermuda Triangle for centuries, a fear which grows as the Sargassum does. Ultimately, Taylor Swift might have said it best when she sang “It’s me, hi, I’m the problem, it’s me.” Our impact on the ecosystem Sargassum lives in is huge.

So, just in case we needed another reason to clean up our act, we can add preventing the growth of the Bermuda Triangle to the list. But we’re not all bad Some people are really lovely And choose to support free access To educational information Through the SciShow Patreon Patrons make it so that these are videos are free For everybody, whether or not you can afford to pay for them You can become a SciShow Patron Today By visiting patreon.com/scishow And choosing whichever level makes sense for you Thank you so much for Watching and learning with us And if you’re watching like 70 years in the future Taylor Swift was like This really big pop-star at the moment And she had this song That’s what we were referencing [ OUTRO ]