Pleurosigma simonsenii

Division: Bacillariophyta
Class: Bacillariophyceae
Order: Naviculales
Species name: Pleurosigma simonsenii Hasle
Synonyms: Pleurosigma planctonicum Simonsen (non P. planctonicum Cleve-Euler)
Common name: A pennate diatom
Date of introduction and origin
Pleurosigma simonsenii was first detected in the English Channel during 1966 and is thought to originate from the Indian Ocean (Simonsen 1974; Boalch & Harbour 1977a; Wallentinus in press).
Method of introduction
The method of introduction is not known, but ballast transport cannot be ruled out (Wallentinus in press).
Reasons for success
Rate of spread and methods involved
It was found in the English Channel (off Ushant, on the French coast) in 1966; and off The Netherlands by 1974 (Wallentinus in press). The method of spread is unknown.
It has been sporadically reported in the English Channel and southern North Sea, but it may have more or less disappeared since these reports were received (Wallentinus in press; Smayda 1990; Interrnational Council for the Exploration of the Sea 1983).
Factors likely to influence spread and distribution
Effects on the environment
Presumably Pleurosigma simonsenii has displaced native species at times since it was reported dominant in the Plymouth area in 1973; it has since 'settled down' to a minor constituent of the plankton (Boalch & Harbour 1977b; Boalch 1987; Wallentinus in press).
Effects on commercial interests
Control methods used and effectiveness
None used.
Beneficial effects
None known.
Currently it is considered a minor constituent of the British phytoplankton (Boalch & Harbour 1977a).
Boalch, G.T. 1987. Changes in the phytoplankton of the western English Channel in recent years. British Phycological Journal, 22: 225-235.
Boalch, G.T., & Harbour, D.S. 1977a. Observations on the structure of the planktonic Pleurosigma. Nova Hedwigia, Beiheft, 54: 275-280.
Boalch, G.T., & Harbour, D.S. 1977b. Unusual diatom off the coast of south-west England and its effect on fishing. Nature, 269: 687-688.
ICES, 1983. Report of the Working Group on Introductions and Transfers of Marine Organisms, Bergen, Norway, 10-13 May 1983. CM 1983/F:27. International Council for the Exploration of the Sea.
Simonsen, R. 1974. The diatom plankton of the Indian Ocean Expedition of R/V "Meteor" 1964-1965. "Meteor" Forschungsergebnisse, Reihe, D. 19: 1-107.
Smayda, T.J. 1990. Novel and nuisance phytoplankton blooms in the sea: evidence for a global epidemic. In: Toxic marine phytoplankton, Granéli, E, Sundström, B., Elder, L., & Anderson, D.M. eds. Proceedings of the Fourth International Conference on Toxic Marine Phytoplankton, 26-30 June 1989, Lund, Sweden. Elsevier, New York, p29-40.
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 (contributors)
Prof. G.R. Hasle, University of Oslo.