This is certainly not how you imagined your beach vacation in Playa del Carmen. Picture: Matheus Bertelli

At the end of May 2025, the Sargassum Observation System (SaWS) of the University of South Florida measured a record amount of Sargassum in the entire Caribbean region. Only the Gulf of Mexico had previously observed similar quantities of brown algae.

Based on previous years’ experience and forecasts, the amount of sargassum will continue to increase over the course of June.

Experts do not expect a more sustained recovery in the situation until the hurricane season, after which the brown algae situation usually eases again in November.

While earlier theories on the Atlantic Sargassum Belt were based on an excess of nutrients originating from intensive agriculture and entering the sea via the Congo, Amazon and Mississippi rivers, scientists in Florida now have a different theory: While they concede that inputs from agriculture are a factor in the formation of Sargassum, they have identified the main source as a seasonal phenomenon known as ‘vertical mixing’, in which shifting winds stir up the ocean and bring nutrient concentrations from the deep sea to the surface.

We recommend (as we do every year) that you avoid the Caribbean beaches during the months of May to October so as not to be disappointed and be confronted with smelly brown piles instead of a white dream beach.