Basque Beret

Overview

Codium bursa, commonly known as the Basque Beret, is a distinctive green marine alga recognized by its unique, sponge-like spherical form. It is widely distributed across the Mediterranean Sea and the northeastern Atlantic Ocean, where it thrives in well-lit, rocky environments.

Appearance

This alga typically begins its life cycle as a solid, dark green sphere. As it matures, it develops into a hollow, water-filled structure that can reach diameters of up to 40 cm. Its surface has a characteristic velvety texture, created by a dense layer of microscopic, club-shaped filaments called utricles. While young specimens are perfectly round, older individuals often become flattened or depressed in the center, earning them their common name, which refers to the shape of a traditional Basque beret.

Distribution & habitat

Codium bursa is found throughout the Mediterranean and in the northeastern Atlantic, ranging from the British Isles and Ireland down to the Canary Islands. It is a photophilic species, meaning it prefers well-illuminated areas, and is commonly found attached to solid rocky substrates. While it can be found in shallow waters, it is known to inhabit depths of up to 50 meters. In the Mediterranean, it is frequently observed in association with Posidonia oceanica seagrass meadows.

Biology & behavior

This species is a perennial organism that grows slowly, often persisting for over a decade in stable conditions. Its internal structure consists of a network of siphonous filaments that enclose a central, water-filled lumen. The alga is highly efficient at absorbing sunlight, which supports its photosynthetic activity. When aging, the thallus may fragment, which can facilitate vegetative regrowth.