A picture taken with a drone shows a spot on the sea surface caused by micro-algae near Tabaiba beach, off the coast of El Rosario on the Spanish Canary island of Tenerife. Photograph: Desiree Martin/AFP/Getty Images

Tourists have been warned to avoid blooms of toxic micro-algae that have been proliferating in hot weather in the sea off Spains Canary Islands.

Tenerife in particular is awash with visitors at this time of year but some of those having a dip in the Atlantic ocean have come out scratching themselves after brushing up against the tiny algae.

The spreading algae have produced a greenish-brown hue in the waters off some beaches in the tourist haven.

Since the end of June we have seen episodes of massive efflorescence, or bloom, of microalgae, sometimes reaching as far as bathing beaches, said Jose Juan Aleman, director of public health for the Canaries.

The algae are a type of bacteria, trichodesmium erythraeum, also known as sea sawdust, said Aleman.

Its proliferation is a natural, temporary phenomenon which is going to disappear in due course, he added, suggesting global warming was helping the algae spread.

The bacterium contains a toxin which can lead to skin irritation, dermatitis, hence one must avoid coming into contact with it in the water and on the sand.

With the islands last year welcoming more than 13 million foreign tourists, local authorities were keen to reassure sun-seekers.

Generally it has not been necessary to close the beaches, said Aleman.

However, AFP found that several have been closed to swimmers over recent weeks, including the popular Teresitas beach at Santa Cruz de Tenerife.

Marta Sanson, professor of plant biology at Tenerifes La Laguna university, said that ideal conditions are allowing proliferation of these micro-algae.

Those include an increase in water temperature as well as a dust cloud sweeping in off the Sahara which is rich in iron, a nutrient which micro-organisms like.

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Canary Island tourists warned to avoid toxic 'sea sawdust' algae - The Guardian