Polysiphonia harveyi
Date of introduction and origin
Polysiphonia harveyi was introduced before 1908 onto
the south coast of England, possibly from northern France where it
was found in 1832 (Maggs & Hommersand 1993). This species may
have originated in the Pacific Ocean and was possibly introduced
from Japan.
Method of introduction
It was an associated unintentional introduction with
oysters.
Reasons for success
It has a rapid growth rate and is an opportunist.
Rate of spread and methods involved
Its rate of spread is not known. There is a small chance it
may have spread through drifting with larger weeds on which it is
an epiphyte (Wallentinus in press).
Distribution
It is found on the south and east coasts of England to Essex
and up the western coast to Scotland. European populations occur
from Norway to the Mediterranean, including Ireland (Maggs &
Hommersand 1993).
Factors likely to influence spread and distribution
It is very tolerant of temperature changes.
Effects on the environment
It possibly displaces native species as it can become very
abundant.
Effects on commercial interests
It is a fouling agent as it is abundant in marinas on
artificial structures, but as it is small, this is not a
significant problem.
Control methods used and effectiveness
None used.
Beneficial effects
None known.
Comments
Japanese populations are interfertile with British populations
of Polysiphonia harveyi (C.A. Maggs pers. comm.), but the
correct taxonomy is still to be determined, possibly involving
Polysiphonia strictissima (described from New Zealand).
All species of Polysiphonia require microscopic
examination to confirm their identification.
References
Maggs, C.A., & Hommersand, M.H. 1993. Seaweeds of the
British Isles. Volume 1: Rhodophyta. Part 3A:
Ceramiales. London, HMSO, for Natural History Museum.
Wallentinus, I. In press. Status of introductions of
non-indigenous marine species to north Atlantic waters:
introductions and transfers of plants. ICES co-operative
research report.
Acknowledgements (contributions from questionnaire)
Dr C.A. Maggs, Queen's University of Belfast.