MEXICO CITY - Tourists looking for sun and sand in Mexican resorts like Cancun, Playa del Carmen and Tulum have been disgusted by foul-smelling mounds of sargassum -- a seaweed-like algae -- piling up on beaches and turning turquoise waters brown.

Experts are warning this could be the new normal.

Mexico's Riviera Maya Caribbean coast provides half the country's tourism revenues and very little sargassum reached it prior to 2014.

But a possible combination of climate change, pollution from fertilizers and ocean flows and currents carrying the algae mats to the Caribbean has caused the problem to explode.

Some officials are saying that while it may not have the global impact of melting of polar ice, the vast mats of sargassum filling the Caribbean could be one of the more visible climate-change events because of the sheer number of people who visit the region's popular tourist beaches.

The government of Mexico's resort-studded coastal state of Quintana Roo calls this one of the biggest challenges that climate change has caused for the world.

It says it requires a joint, multinational effort and a global commitment.

While tourist arrivals at the Cancun airport were up 3.3 per cent in March over the same month last year, many fear it won't last long with the sargassum befouling white sand beaches and blue waters.

Then there's the air -- sargassum decomposes with a rotten egg smell.

As it decays and sinks to the bottom, it can also smother the coral the Caribbean is known for, and accumulations on beaches can make it harder for sea turtles to nest.