Green Sea-fingers, Codium fragile fragile is a spongy green seaweed with numerous Y-shaped, branching, cylindrical fronds extending to about 25 cm. The fronds have a felt-like texture and a disc-shaped holdfast formed from many fine filaments. It can only be distinguished from native Codium tomentosum by microscopic examination.
Native to the Pacific around Japan and Korea it first appeared in Devon in 1939 growing on oyster shells. This species is found on rock and coralline algae in pools and on open rock from the mid to lower shore, and subtidally to depths of fifteen metres. On sandy or muddy shores it attaches to bivalve shells, rocks or artificial structures. It mainly inhabits protected bays and estuaries but also occurs on semi-exposed shores.
Its most significant impact on native marine flora has occurred where algal diversity in the invaded area is low. In Britain algal diversity is high and green sea fingers has not yet occurred in densities high enough to cause problems. At high densities it can be a fouling nuisance in shellfish beds, smothering mussels and scallops, clogging scallop dredges and interfering with harvesting. It also fouls boats, fishing nets, wharf pilings and jetties.
Information and Identification Sheets: Green Sea-fingers