Kevin Murphy k.murphy@bio.gla.ac.uk

1. INVASION OF LOCH LOMOND, SCOTLAND BY ALIEN ELODEA SPECIES Kevin Murphy1 & Sandrine Picq2 1University of Glasgow, Scotland; 2Ecole Nationale Supérieure d’Agronomie de Montpellier, France One of the largest lakes in the British Isles, Loch Lomond is an important freshwater asset for potable water supply, recreation and amenity, hydroelectric power generation, and as a habitat supporting aquatic biodiversity, including breeding populations of rare fish such as the brook lamprey (Lampetra planeri) and powan (Coregonus clupeoides: a non-migratory member of the salmon family, only two populations of which occur in Scotland), plus a diverse flora of native submerged aquatic macrophytes. In differing degree, all these functions are threatened by invasion of two submerged aquatic weed species originating in North America; first Elodea canadensis, and more recently Elodea nuttallii (Murphy et al 1994; Macleod & Murphy 2002). In 2007 a quantitative survey of 42 sites within Loch Lomond recorded 20 macrophyte species, and showed that within the lake as a whole, Elodea nuttallii was co-dominant with three native species (Littorella uniflora, Isoetes lacustris and Myriophyllum alterniflorum). Elodea canadensis was a minor component of the flora and has declined sharply since surveys early in the 1990s. Four separate communities of aquatic plants were identified by TWINSPAN classification analysis. Three were indicated by native species only: Callitriche hamulata (at 7% of sites); M. alterniflorum (14%); and a mixed community of L. uniflora, I. lacustris and Potamogeton perfoliatus (40%). The fourth (38%) was co-dominated by L. uniflora and Elodea nuttallii: and was predominantly located in shallow areas of the loch sheltered from wind and wave action, where the tall, sub-surface canopy forming stands of E. nuttallii were clearly at a competitive advantage. The evidence suggests that E. nuttallii has increased both its distribution and abundance in the Loch since the previous survey, in 2000, but it may be approaching a more stable state, preferentially occupying a clearly-defined habitat type within the lake ecosystem, at the expense of native species which occur in sheltered areas. Unfortunately, such areas of the lake are heavily favoured for tourist use (especially boat mooring, sailing and kayaking, miscellaneous shoreline recreation, and fishing), all of which are interfered with by dense growths of E. nuttallii. There is likely to be an ongoing need for localized weed control efforts, using physical or chemical approaches (e.g weed clearing boats; dichlobenil treatments), in such areas to reduce E. nuttallii problems to manageable levels. Boat moorings: Loch Lomond Underwater photo of Elodea stands overgrowing Littorella in Loch Lomond References Macleod H, Murphy KJ, 2002. Temporal and distributional variation in submerged macrophyte communities of Loch Lomond, Scotland. Proc. 11th EWRS International Symposium on Aquatic Weeds, France, pp. 39 - 42 . Murphy KJ, Hudson KD, Mitchell J, 1994. Freshwater and wetland plant communities of Loch Lomond. Hydrobiologia 290, 63 - 74. Kevin Murphy k.murphy@bio.gla.ac.uk