Codium fragile

Division: Chlorophyta
Class: Chlorophyceae
Order: Codiales
Species name: Codium fragile (Suringar) Hariot subsp. tomentosoides (van Goor) Silva
Synonyms: None
Common name: Green sea fingers
Date of introduction and origin
Codium fragile subsp. tomentosoides  was introduced from mainland Europe to the River Yealm, Devon, in 1939 where it was first found at Steer Point (Silva 1955). This species originated in the Pacific Ocean around Japan.
Method of introduction
It spread remotely either as an associated unintentional introduction attached to shellfish such as oysters, attached to ships' hulls or as spores in ballast tanks; and marginally through rafting and floating.
Reasons for success
Lack of grazers has probably contributed to its success. It is an opportunist, exhibiting vegetative propagation and perennation.
Rate of spread and methods involved
This species was first collected in Holland in 1900 (van Goor 1923 quoted by Silva 1955) and has spread from Devon to Scotland since 1939 through marginal, natural dispersion by rafting and floating (I. Tittley pers. comm.). In Europe the initial spread was slow from the Netherlands but speeded up in the 1940s, possibly due to wartime shipping. Burrows (1991) considered it has spread fairly rapidly from the south coast northwards since its initial discovery.
It is distributed throughout Britain, but particularly along the south coast of England and the west coast of Scotland (Hardy 1981; Hardy 1990; Irvine et al. 1975; South & Tittley 1986). Elsewhere in Europe it occurs on the south and west coasts of Ireland, the western Mediterranean and from Atlantic Spain (I. Fuller pers. comm.) to Norway.
Factors likely to influence spread and distribution
Temperature is likely to be a limiting factor to this species.
Effects on the environment
It displaces native species Codium tomentosum (Farnham 1980) although there is some recent indication that the native Codium tomentosum is making a comeback against this non-native (W.F. Farnham pers. comm.).
Effects on commercial interests
It is used as a food in the Far East.
Control methods used and effectiveness
None used.
Beneficial effects
None known.
See comments on C. fragile subsp. atlanticum.
Burrows, E.M. 1991. Seaweeds of the British Isles. Volume 2. Chlorophyta. London, Natural History Museum.
Farnham, W.F. 1980. Studies on aliens in the marine flora of southern England. In: The shore environment, volume 2: ecosystems, ed. by J.H. Price, D.E.G. Irvine & W.F. Farnham, 875-914. London, Academic Press. (Systematics Association Special Volume, No. 17B.)
Hardy, F.G. 1981. Codium on the Northumbrian coast. Transactions of the Natural History Society of Northumbria, 43: 59-60.
Hardy, F.G. 1990. The green seaweed Codium fragile on the Berwickshire coast. History of the Berwickshire Naturalists' Club, 44: 154-156.
Irvine, D.E.G., Guiry, M.D., Tittley, I., & Russell, G. 1975. New and interesting marine algae from the Shetland Isles. British Phycological Journal, 10: 57-71.
Silva, P.C. 1955. The dichotomous species of Codium in Britain. Journal of the Marine Biological Association of the United Kingdom, 34: 565-577.
South, G.R., & Tittley, I. 1986. A checklist and distributional index of the benthic marine algae of the North Atlantic Ocean. St Andrews & London, Huntsman Marine Laboratory & British Museum (Natural History).
Acknowledgements (contributions from questionnaire)
Dr F.G. Hardy, University of Newcastle-upon-Tyne.
Mr I. Tittley, Natural History Museum, London.
Dr C.A. Maggs, Queen's University of Belfast.