Codium bursa (Olivi) C.Agardh

Also known as Green Sponge Ball or Ball Alga (English) or Basque Beret (French).

Description: Grass green to blue-green, 10-400 mm wide. Velvety surface firm to touch, solid and spherical when young; maturing to form undulating, converging growths. Becoming hollow and water-filled with age. Composed of intertwined, microscopic filaments terminating in utricles visible as small bumps on surface with a hand-lens.

Habitat: subtidal on rock to 10 m in Atlantic and to 50 m in Mediterranean.

Distribution: Ireland (two locations Cos Donegal and Galway) and England; south to Morocco and Canary Islands. Widespread in Mediterranean and often accompanying the seagrass Posidonia oceanica and common in drift in some locations amongst Posidonia leaves. Reports from New Zealand uncertain. Note: There are no recent records from England, and many earlier records were of drift specimens perhaps originating further south as the plants are very persistent in drift.

Picture © Lin Baldock, Leitir Calaidh, Co. na Gaillimhe [Lettercallow, Connemara, Co. Galway] shallow subtidal.