Description
Egeria densa is a submersed plant (submersed aquatic vegetation, SAV).
Potentially Misidentified Species - Elodea nuttalli is regarded as a synonym of E. canadensis by some authors. Catling and Wojtas (1986) give criteria for separating it from E. canadensis; both are native.
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Plantae | Magnoliophyta | Liliopsida | Hydrocharitales | Hydrocharitaceae | Egeria |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1915 | Established | Stable | Introduced | Regular Resident | South America | South America | Ornamental(Aquatic Plant) |
History of Spread
Egeria densa (Brazilian Waterweed) is native to South America, from southeast Brazil to Argentina, but has been widely introduced throughout the world (Cook and Urmi Konig 1984). It was widely sold as an aquarium and fishpond 'oxygenator' plant from the early days of the aquarium trade to the present. It rapidly spread through subtropical and warm-temperate regions of United States, and became widespread, reaching MA by 1923, then FL (1924), CA (1938) and eventually the Canadian border at British Columbia and Ontario (Catling and Wojtas 1985). It was first reported from the San Francisco Bay Delta in 1979 (Cohen and Carlton 1995). Egeria densa is now found from NH to FL and across the southern half of IL, NE, UT, and up to Pacific coast to WA (Natural Resources Conservation Service 1998). It has been introduced in Europe north to Denmark, and also to Japan, Australia, New Zealand, Africa, Central America, and northern South America (Cook and Urmi Konig 1984).
James River - Egeria densa was recorded from the nontidal drainage in 1937 ['Dominant in argillaceous border of millpond', Dinwiddie County (Fernald 1938)]. In the 1960's-70's, it caused weed problems in Walker Dam Reservoir on nontidal Chickahominy River (United States Army Corps of Engineers 1977).
Potomac River- The first record of E. densa from the nontidal drainage is from Ammendale (near Beltsville), Prince George's County MD, in 1915 (U. S. National Herbarium collections). It was found in small coves, and tidally flushed ponds in fresh water only (Haramis and Carter 1983); near Dyke Marsh, Alexandria VA (Carter et al. 1984), but was not recorded in most general submerged aquatic vegetation surveys (e.g. Orth et al. 1987; Orth et al. 1993).
Eastern Shore Tributaries - It was collected in the tidal Wicomico River; Salisbury MD in1938 (Tatnall 1946), but not reported there in recent surveys (Orth et al. 1993).
History References - Carter et al. 1984; Catling and Wojtas 1985; Cohen and Carlton 1995; Cook and Urmi Konig 1984; Fernald 1938; Haramis and Carter 1983; Natural Resources Conservation Service 1998; Orth et al. 1993; Tatnall 1946; United States Army Corps of Engineers 1977; U. S. National Herbarium collections
Invasion Comments
Vector(s) of Introduction: Egeria densa could be spread by recreational boats and trailers, as an alternate vector.
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 1.0 | 32.0 | 16.0 | 28.0 |
| Salinity (‰) | 0.0 | 0.0 | 0.0 | |
| Oxygen | hypoxic | |||
| pH | 6.4000000000 | 9.2000000000 | ||
| Salinity Range | fresh-oligo |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | ||
| Typical Adult Size (mm) | ||
| Maximum Adult Size (mm) | 1000.0 | 1000.0 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
|||
| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
|||
| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Effects of Egeria densa (Brazilian Waterweed) are limited by its restricted distribution in the Bay. This plant is very local in tidal waters (Carter et al. 1984), but E. densa caused weed problems in Walker Dam Reservoir on nontidal Chickahominy River in the 1960's. Interference with fisheries, boating, duck hunting, and use of the reservoir for drinking water (for the city of Newport News) were noted. A control program cleared the reservoir in 1967-69, but a reinfestation occurred in 1973 (United States Army Corps of Engineers 1977).
References - Carter et al. 1984; United States Army Corps of Engineers 1977
Economic Impacts Outside of Chesapeake Bay
Egeria densa (Brazilian Waterweed) spreads rapidly and is widespread in the southeast United States (Godfrey and Wooten 1979) and throughout warmer regions of the world. However, it has been described as 'rarely more than a nuisance' (Cook and Urmi-Konig 1984). It 'only occasionally causes problems' in Florida (McCann et al. 1995). However, E. densa is listed as a noxious weed in at least 3 states (Natural Resources Conservation Service 2001).
References - Cook and Urmi Konig 1984; Godfrey and Wooten 1979; McCann et al. 1995; Natural Resources Conservation Service 2001
Ecological Impacts on Chesapeake Native Species
Egeria densa (Brazilian Waterweed) appears to be rare and scattered in tidal tributaries of Chesapeake Bay, probably because this species grows slowly under turbid condtions (Barko and Smart 1981). Consequently, it has no reported impacts in the Bay proper, although it has become abundant in reservoirs in the watershed (United States Army Corps of Engineers 1977).
Competition - Egeria densa often produces large monospecific stands in favorable environments (Cook and Urmi Konig 1984), but is poorly adapted to turbid conditions (Barko and Smart 1981; Carter et al. 1984). Egeria densa is probably also limited by a low salinity tolerance, since we found no information on its occurrence in saline waters. Egeria densa is listed as invasive in DE and VA (Delaware Natural Heritage Program 1998; Virginia Department of Conservation and Recreation 1999).
Habitat change - Where abundant, E. densa provides cover for fishes; habitat for epiphytic invertebrates (see Hydrilla verticillata).
Food/Prey - Egeria densa is eaten by waterfowl, but its food value is limited by lack of seeds (Hurley 1990).
References - Barko and Smart 1981; Carter et al. 1984; Cook and Urmi Konig 1984; Delaware Natural Heritage Program 1998; Hurley 1990; United States Army Corps of Engineers 1977; Virginia Department of Conservation and Recreation 1999
Ecological Impacts on Other Chesapeake Non-Native Species
Egeria densa (Brazilian Waterweed) appears to be rare and scattered in tidal tributaries of Chesapeake Bay, probably because this species grows slowly under turbid conditions (Barko and Smart 1981) . Consequently, it has no reported impacts in the Bay proper, although it has become abundant in reservoirs in the watershed (United States Army Corps of Engineers 1977). In tidal freshwater portions of the San Francisco estuary, dense growths of these plants have had severe impacts on habitat and foodwebs (Moyle et al. 2010). Competition - Hydrilla verticillata (Hydrilla) has better growth and photosynthesis under turbid, low-light conditions (Barko and Smart 1981) and probably is more salt-tolerant (Haller et al. 1974; Twilley and Barko 1990). Myriophyllum spicatum (Eurasian Watermilfoil) grows more slowly under all light conditions, but is more tolerant of salinity (Barko and Smart 1981; Twilley and Barko 1990). Food/Prey - Egeria densa is eaten by Ctenopharyngodon idella (Grass Carp) (Shireman and Smith 1983) and probably also by Cyrinus carpio (Common Carp). References - Barko and Smart 1981; Haller et al. 1974; Shireman and Smith 1983; Twilley and Barko 1990
References
Barko, John W.; Smart, R. Michael (1981) Comparative influences of light and temperature on the growth and metabolism of selected submersed freshwater macrophytes, Ecological Monographs 51: 219-235Carter, Virginia; Gammon, Patricia T.; Bartow, Nancy C. (1984) Submersed aquatic plants of the tidal Potomac River, Geological Survey Bulletin 1543: 1-58
Catling, Paul M.; Wojtas, Walter (1986) The waterweeds (Elodea and Egeria) in Canada, Canadian Journal of Botany 64: 1525-1541
Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, , Washington DC, Silver Spring MD.. Pp.
Cook, Christopher D. K.; Urmi-König, Katharina (1984) A revision of the genus Egeria, Aquatic Botany 19: 73-96
1998 Non-native plant species in Delaware. http://www.dnrec.statede.us/iw/weeds.htm
Fernald, Merritt L. (1938) Noteworthy plants of southeastern Virginia, Rhodora 40: 364-424, 434-485
Godfrey, R. K.; Wooten, Jean W. (1979) Aquatic and Wetland Plants of the Southeastern United States: Monocotyledones., In: (Eds.) . , Athens. Pp.
Haller, William T.; Sutton, D. L; Barlowe, W. C. (1974) Effects of salinity on the growth of several aquatic macrophytes, Ecology 55: 891-894
Haramis, G. M.; Carter, V. (1983) Distribution of submersed aquatic macrophytes in the tidal Potomac River, Aquatic Botany 15: 65-79
Harvill, A. M.; Bradley, Ted R.; Stevens, Charles E.; Wieboldt, Thomas F.; Ware, Donna M. E.; Ogle, Douglas W.; Ramsey, Gwynn W.; Fleming, Gary P. (1992) Atlas of the Virginia Flora, , Burkeville, VA. Pp.
Hotchkiss, Neil (1967) Underwater and floating-leaved plants of the United States and Canada, Bureau of Sport Fisheries and Wildlife, Resource Publication 44: 1-124
Hurley, Linda M. (1990) Field guide to the submersed aquatic vegetation of Chesapeake Bay., , Annapolis, MD. Pp.
Muenscher, Walter C. (1944) Aquatic plants of the United States., In: (Eds.) . , Ithaca NY. Pp.
1997-2024 USDA PLANTS Database.. Onine databse
Orth, Robert J.; Nowak, Judith F.; Anderson, Gary F.; Whiting, Jennifer R. (1993) Distribution of submerged aquatic vegetation in the Chesapeake Bay and Tributaries and Chincoteague Bay - 1992, , Annapolis, MD. Pp.
Resource Management Inc. (1993) National list of plant species that occur in wetlands., , Minneapolis.. Pp.
Shireman, Jerome V.; Smith, Charles R. (1983) Synopsis of biological data on the grass carp Ctenopharynogodon idella (Cuvier and Valenciennes, 1844), , Rome. Pp.
Tatnall, Robert R. (1946) Flora of Delaware and the Eastern Shore, , Wilmington. Pp.
Twilley, Robert R.; Barko, John W. (1990) The growth of submersed macrophytes under experimental salinity and light conditions, Estuaries 13: 311-321
United States Army Corps of Engineers (1977) Chesapeake Bay Future Conditions Report, , Baltimore. Pp.
1999 Invasive Alien Plant Species of Virginia. http://www.state.va.us/~dcr/dnh/invlist.htm