A Pacific invasive red alga, Rugulopteryx okamurae, has now crossed into the…

A Pacific invasive red alga, Rugulopteryx okamurae, has now crossed into the protected waters of Arrábida, marking a decisive new threshold in its year-long advance down the Portuguese coast. First documented inside the park on June 28, the species arrived after moving steadily south from Cascais through Estoril, Paço de Arcos, and Sesimbra—a progression that took less than a year. It smothers the rocky reefs and Neptune grass beds that are the structural backbone of this coast.

Summer is peak growing season, and the alga spreads in fragments via dive gear and boat traffic, making even careful recreational use a vector for its expansion. Twenty-two observations across the year show the acceleration of its range, and with established populations now inside a major marine protected area, containment has become far more difficult. What matters now is whether the Mediterranean-adapted reef communities here can adapt faster than this warm-water invader spreads.