Invasive Alien Species in Belgium: Egeria densa

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Egeria densa - Brazilian waterweed

ISSG RISK ANALYSIS

Synonym:	Elodea densa
French name:	Egéria
Dutch name:	Egeria
Family:	Hydrocharitaceae

Group:	Vascular plants
Origin:	South America
Habitat:	freshwater
Introduction:	aquariums and ponds

ISEIA Score : 12

Naturalization in Belgium

First observation in the wild:	1999
Invasion stage:	spread
Spatial distribution:	isolated

Invasiveness

Reproduction in the wild:	yes
Dispersion potential:	high
Natural habitats:	high

More on invasiveness: The Brazilian waterweed as a very wide ecological amplitude. It thrives in various types of freshwater habitats, from acid to eutrophic environments. It prefers flowing systems but may also be found in still waters. This aquatic weed is not light demanding and is able to develop in deep and turbid waters.

Distribution in Belgium

Established populations Biogeographic areas where the species is known to be established in the wild

	absent from district
	isolated populations (1-5 localities per district)
	widespread (>5 localities per district)

Endangered areas Biogeographic areas including Natura 2000 habitats that are likely to be invaded by the species (occurence of dense populations)

Biogeographic areas including Natura 2000 habitats that are likely to be invaded by the species (occurence of dense populations)

	low risk
	medium risk
	high risk

Endangered Natura 2000 habitats (

freshwater habitats:

3260

Impacts on Species

Predation / Herbivory:	low
Competition:	high
Disease transmission:	low
Genetic effects:	low

Impacts on Ecosystems

Nutrient cycling:	high
Physical alteration:	high
Natural successions:	high
Food web alteration:	low

More on impacts: Egeria densa is highly competitive in meso-eutrophic waters. As observed for most non-native Hydrocharitaceae species, this submerged perennial aquatic plant makes dense monospecific populations which often colonise all of water bodies, restrict water movement, cut off light, produce anoxic conditions and trap sediments in the system. The Brazilian waterweed has been reported to outcompete native aquatic plants and to adversely affect fish communities. Dense beds provide a poor habitat for aquatic animals and are not consumed by fish. They interfere with recreation activities and increase the risk of adjacent land flooding.

Data Source & References

Authors:	Branquart Etienne, Stiers Iris, Triest Ludwig, Vanderhoeven Sonia, Van Landuyt Wouter, Van Rossum Fabienne, Verloove Filip
Published on:	22 November 2007
Last update:	11 December 2013

References:

Denys, L., Packet, J. & Van Landuyt, W. (2004)

Neofyten in het Vlaamse water : signalement van vaste waarden en rijzende sterren.

Natuur.focus 3(4): 120128.

ISSG (Invasive Species Specialist Group) (2006)

Online fact sheets

Global Invasive Species Database, IUCN.

Lambinon, J., Delvosalle, L. & Duvigneaud, J. (2004)

Nouvelle fore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des régions voisines.

Editions du Patrimoine du Jardin botanique national de Belgique, Meise.

Mony, C.,Koschnick, T.J., Haller, W.T. & Muller, S. (2007)

Competition between two invasive Hydrocharitaceae (Hydrilla verticillata (L.f.) (Royle) and Egeria densa (Planch)) as influenced by sediment fertility and season.

Aquatic Botany 86: 236–242.

Muller, S. (2004)

Plantes invasives en France : état des connaissances et propositions d'actions.

Publication scientifique du Museum d'Histoire naturelle, Patrimoines naturels n°62.

Thiébaut, G. (2007)

Non-indigenous aquatic and semiaquatic plant species in France.

In: F. Gherardi (Ed.), Biological invaders in inland waters: profiles, distribution and threats, Springer: 209-229.

Toussaint, B. & Bedouet, F. (2005)

Les espèces végétales invasives des milieux aquatiques et humides du bassin Artois-Picardie.

Agence de l'Eau Artois-Picardie, 38 pp.

Verloove, F. (2006)

Catalogue of the Neophytes in Belgium (1800-2005).

Scripta Botanica Belgica 39, 89 pp.

Washington State Department of Ecology (2003)

Technical information about Egeria densa (Brazilian Elodea).

Water Quality Program: Non-Native Freshwater Plants.

Weber, E. (2003)

Invasive plant species of the world: a reference guide to environmental weeds.

CABI Publishing, Cambridge, Massachusetts, 548 pp.