The fast-growing invasive seaweed choking New Zealand’s coastline

‘The frightening thing about it is its speed of growth’. Caulerpa exotic seaweed threatens New Zealand’s exotic marine environment. It was first detected around the coast of Aotea/Great Barrier Island in Auckland’s Hauraki Gulf in 2021. Photograph: Glenn Edney

Caulerpa, a virulent exotic seaweed that forms dense mono-cultural mats across the seafloor, is marching along parts of New Zealand’s coast, prompting fears it could become the worst ever threat of an invasive species to the local marine environment.

Caulerpa can grow up to 3cm a day, in warm, clear, shallow waters, creating a green carpet across the seafloor and enveloping everything in its path. It competes with native seaweeds and sea grasses, smothers shellfish and can shrink the diversity of marine life.