Beaches in Mexico are becoming overwhelmed by foul-smelling sargassum, a seaweed-like alga that experts have said could be the new normal.

The algae has been piling up in huge volumes at some of the most famous resorts, including Cancun, Playa del Carmen and Tulum – not only ruining the beaches, but also turning the turquoise waters brown.

Prior to 2014, the region had very little sargassum, but in recent years, the problem has exploded. The sudden increase is thought to be due to a combination of climate change, pollution from fertilisers and ocean currents carrying the algal mats to the Caribbean.

“We are having the problem in the northern coast of Quintana Roo, where it is more noticeable because it’s where most people live, and where most activities are happening,” said Gonzalo Merediz director of the Sian Ka’an conservation charity, “but we are having the problem in the entire coast of Quintana Roo, as it is happening also in Central America and many islands of the Caribbean.”

Sargassum is a brown alga that forms large floating mats. It usually blooms in the Sargasso Sea, a vast body of water in the north Atlantic, and is a critical habitat for many marine species such as mahi-mahi, tuna, eels and sea turtles.

Sargassum has always washed up along tropical shores in small amounts, but it becomes a problem when it occurs in large amounts.

Severe inundations, known as “harmful algae blooms”, can wipe out fish populations, harm tourism and cause coastal dead zones. As it decays and sinks to the bottom, it can also smother the coral for which the Caribbean is known, and accumulations on beaches can make it harder for sea turtles to nest.

Tourist season

Although tourist arrivals at the Cancun airport were up 3.3 percent in March compared with March last year, many fear the increase will not last because tourists come to Mexico’s Caribbean coast for the sun, sand, snorkelling and turquoise waters.

Gustav, visiting from Calgary, Canada, was just one of the tourists who was not impressed with the algae. “You can’t really swim here, you can’t really spend any time in the water,” he said. “It looks dirty, and it is something that I wouldn’t even risk my own health for.”

Scientists have set up sargassum tracking systems that detect the amount of algae heading for shores in the Caribbean, but it’s hard to predict when or where it will land.

Gonzalo Merediz said that even removing the sargassum from the beaches is not straightforward. Shovelling the sargassum is a Herculean task that raises other concerns, such as where to dump it.

“When the seaweed is extracted from the ocean, and dumped anywhere in the land, specifically here, where we have this limestone that is very permeable, the nutrients of these seaweeds goes into the underground and can affect also the aquifer. So, we have to be very careful about where we put this material that is extracted.”

The Americas is not the only part of the world to be inundated with the stinky sargassum. The coast of West Africa has also seen a huge increase in recent years, with Sierra Leone complaining of a particularly severe influx a few years ago.