In the summer of 2021, it caused the closure of several beaches and created a wave of panic: in the Basque Country, a toxic microalgae is the subject of a cross-border research program, launched this Thursday, April 11, to understand the extent of its development in this region of the North Atlantic.
This toxic microalgae, ostreopsis ovata, had been known to scientists for several years. Initially present in the Mediterranean, it gradually gained ground. Its recent establishment on the Basque coast, both French and Spanish, is however viewed negatively. “This is the first time that we have observed this species on the northern Atlantic coast,” explained Elvire Antajan, researcher at Ifremer (French Research Institute for the Exploitation of the Sea), even if the algae had already been observed as early as 2007, said Jose Ignacio Asensio, deputy for the province of Gipuzkoa.
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The problem really materialized in the summer when this “new arrival in the local landscape” caused the “start of a major crisis”, underlined Emmanuel Alzuri, the mayor of the town and president of an interest group. scientist on the Basque coast, during a press conference in Bidart (Pyrénées-Atlantiques). Several hundred reports of flu symptoms, rhinitis or respiratory tract irritation then alerted local elected officials, who were forced to close the beaches of Biarritz, Bidart and Saint-Jean-de-Luz.
Based on this “immense concern”, the cross-border research program brings together scientists and institutions from both sides of the border, in the Basque Country. Developed over three years on nine coastal sites, it is designed to help political decision-makers develop an alert protocol or even new regulations thanks to a budget of 2.2 million euros, financed by European funds to the tune of 1 .4 million euros.
One of the areas of study consists of understanding the causes of the expansion of this microalgae. According to scientists, its presence, noted in particular on the coast between Bilbao and San Sebastian as far as Biarritz, is a direct consequence of climate change and ocean warming. But several factors also contribute to favoring its growth: the coastal riprap which facilitates its fixation and waters at more than 20 degrees. The toxin contained in the algae can then be released into the sea spray if the body of water is agitated.
