Short description of Elodea nuttallii,

Nuttall's waterweedis an aquatic herb with branching stems <30 cm long with laves in whorls of (2-)3-4 which are widest near the base the middle, tapering to a point and usually strongly twisted except in dense shade.

Impact summary: Elodea nuttallii,

The actual impact of Nuttall's waterweed is difficult to assess; it certainly occupies large areas of the beds of standing and flowing water bodies which might otherwise support native plants.

Habitat summary: Elodea nuttallii,

Nuttall's waterweed is most abundant in nutrient-rich lakes and ponds both in its native and invasive range; however it will also grow in flowing water, even in areas with fast flow, although it rarely forms dense beds in such conditions.

Overview table

Environment	Freshwater
Species status	Non-Native
Native range	Northern America
Functional type	Land plant
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	v.c.23
Date of first record	1966

Origin

Nuttall's waterweed is native to temperate North America, it was first recorded in Europe in Belgium in 1939

First Record

Nuttall's waterweed was first recorded from a ditch at Beard Mill, Stanton Harcourt in 1966.

Pathway and Method

Nuttall's waterweed became established in GB by accidental or deliberate release after import for ornamental purposes in aquaria and ponds. It probably moved from artificial to natural sites as a result of fragments being transported by stock or by man, such as on fishing equipment or boats.

Species Status

Nuttall's waterweed occurs as an alien in Japan (where all populations are male) and continental Europe (where all plants are female), particularly the north and west. Until about 1995, it showed little sign of significant increase, with records from fewer than fifty 10km squares until then. However by 2000 there were records from 800 10km squares, rising to over 1000 today. The most significant increase occurred between 1995 and 2000 and may actually be an artefact of improved identification and increased recording for the atlas.

Dispersal Mechanisms

All plants in the UK are female, although one population involving male plants was recorded near Edinburgh between 1879 and 1903; all dispersal must therefore be by vegetative means and is likely to be by fragments.

Reproduction

Reproduction is almost certainly predominantly from fragments, although turions are produced in the autumn.

Known Predators/Herbivores

Nuttall's waterweed is preyed upon by a high number of freshwater organisms including fish and birds, but none of these have been shown to have a significant effect on Nuttall's waterweed in GB.

Resistant Stages

None known.

Habitat Occupied in GB

Nuttall's waterweed is most abundant in nutrient-rich lakes and ponds both in its native and invasive range; however it will also grow in flowing water, even in areas with fast flow, although it rarely forms dense beds in such conditions.

Nuttall's waterweed is widespread and abundant throughout England south of the Pennines. Outside this area, there are a few localised concentrations but it is mainly absent or scattered.

Environmental Impact

It is difficult to assess the impact of Nuttall's waterweed on natural ecosystems in GB. It typically occurs in more eutrophic water bodies, where it may replace populations of native taxa, but in general it appears to behave as would a native taxon.

Health and Social Impact

None known.

Economic Impact

None known.

Identification

Stace, C.A. (2010) New flora of the British Isles, Third Edition, Cambridge University Press, Cambridge.

Lansdown, R.V. (2009) A field guide to the riverine plants of Britain and Ireland, Ardeola, Stroud, Gloucestershire.

Biology, ecology, spread, vectors

www.nerc-wallingford.ac.ukresearchcapmpdf files25 Elodea nuttallii.pdf

Management and impact

www.nerc-wallingford.ac.ukresearchcapmpdf files25 Elodea nuttallii.pdf

General

www.nerc-wallingford.ac.ukresearchcapmpdf files25 Elodea nuttallii.pdf

https://www.cabi.org/isc/datasheet/20761

https://secure.fera.defra.gov.uk/nonnativespecies/downloadDocument.cfm?id=618