Authorities across the Caribbean are releasing emergency funding to clean up piles of decaying seaweed so huge and pungent that tourists have cancelled summer beach holidays and lawmakers on Tobago have deemed it a “natural disaster”.

The Dominican Republic, Barbados and Mexico’s Yucatan peninsula have also been badly affected in recent weeks, with the sargassum outbreak taking over popular beaches and coves.

The picture-perfect beaches and turquoise waters that people expect from the Caribbean are increasingly being fouled by mats of plant matter that attract biting sand fleas and smell like rotten eggs.

Clumps of the brownish seaweed, known as sargassum, have long washed up on Caribbean coastlines, but researchers say the algae has exploded in extent and frequency in recent years.

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