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| Egeria densa | |
|---|---|
| Name | Egeria densa |
| Status | Invasive |
| Genus | Egeria |
| Species | densa |
| Authority | Planch. |
Egeria densa Egeria densa is a submerged freshwater aquatic plant native to South America that has become a widespread invasive species in North America, Europe, Asia, and Oceania. It is noted for forming dense monospecific stands that alter river and lake ecosystems, impeding navigation and affecting hydropower infrastructure. Management involves mechanical, chemical, and biological approaches implemented by agencies such as the United States Fish and Wildlife Service, Environment Canada, and regional water authorities.
The species was described by Jules Émile Planchon and placed in the genus Egeria within the family Hydrocharitaceae, alongside related genera such as Elodea and Hydrilla verticillata. Synonyms and historical names have included placements under genera used in nineteenth-century botanical works tied to institutions like the Royal Botanic Gardens, Kew and the Muséum national d'Histoire naturelle. Molecular phylogenetic studies referencing sequences submitted to databases curated by organizations like the National Center for Biotechnology Information have clarified relationships among Hydrocharitaceae members described by taxonomists associated with the International Botanical Congress.
Egeria densa produces long, flexible stems with whorls of translucent leaves and pinnate venation similar to species treated in floras from the Missouri Botanical Garden and the Royal Botanic Garden Edinburgh. Diagnostic features used by botanists at the Smithsonian Institution and the Australian National Herbarium include leaf arrangement, flower morphology, and starch storage in rhizoids, distinguishing it from taxa documented in keys by the United States Department of Agriculture and regional manuals used by the California Department of Fish and Wildlife. Flowering is infrequent in temperate regions, with aquatic botanists from universities such as University of California, Davis, University of Queensland, and University of São Paulo recording sporadic reproductive observations.
Native to Brazil and Argentina, the species has been transported globally through the aquarium trade networks centered in places like Hong Kong, Amsterdam, and Los Angeles. It now occurs in freshwater systems monitored by agencies including the European Environment Agency, New Zealand Ministry for Primary Industries, and state-level departments such as the Florida Fish and Wildlife Conservation Commission and the Victorian Department of Environment, Land, Water and Planning. Preferred habitats encompass slow-moving rivers, ponds, lakes, and reservoirs altered by projects like the Three Gorges Dam and managed by authorities such as the Tennessee Valley Authority.
Egeria densa propagates primarily through vegetative fragmentation, a life history strategy studied by ecologists at institutions such as Stanford University, Monash University, and University of Buenos Aires. It alters nutrient cycling and light regimes in systems monitored by research programs at the International Union for Conservation of Nature and the Scientific Committee on Problems of the Environment. Interactions with fauna include provision of habitat for invasive fishes recorded by the Florida Fish and Wildlife Research Institute and impacts on native macrophytes documented by the European Commission's aquatic vegetation surveys. Seasonal growth patterns have been linked to water temperature and photoperiod effects investigated by researchers at the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution.
The species causes economic and ecological impacts similar to invasive plants assessed by the World Bank and mitigation strategies promoted by the Convention on Biological Diversity. Impacts include obstruction of navigation affecting commercial operations in ports like Port of Antwerp and recreational boating managed by local authorities in regions such as California and Victoria (Australia). Management techniques evaluated in trials by the United States Army Corps of Engineers, CABI, and university extension services include mechanical harvesting used by municipal utilities in Melbourne and herbicide application guided by regulators such as the Environmental Protection Agency. Biological control research has referenced potential agents investigated through collaborations involving the Commonwealth Scientific and Industrial Research Organisation and university entomology departments, while prevention relies on policies implemented by border agencies including US Customs and Border Protection.
Egeria densa entered global distribution through the ornamental aquarium trade and is commonly sold in markets in cities like Tokyo, Barcelona, and São Paulo. It has been used in laboratory settings for physiology experiments at research centers such as the Max Planck Society and classrooms affiliated with the University of Oxford and Harvard University for photosynthesis and gas exchange demonstrations. Some wastewater treatment projects evaluated by the United Nations Environment Programme and municipal authorities have trialed macrophyte-based remediation incorporating this species, though many regulatory bodies including the European Union and state departments have restricted sale and transport due to invasive risk.
Category:Hydrocharitaceae Category:Invasive species