Codium fragile
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.
Distribution
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.
Comments
See comments on C. fragile subsp.
atlanticum.
References
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.