Description
Myriophyllum spicatum (Eurasian Watermilfoil) is a submersed plant (submersed aquatic vegetation).
Synonymy - Some MD authors, eg. Brown and Brown (1984); Krauss et al. (1971) have included this species in M. exalbescens Fernald (now known as M. sibiricum Komarov).
Potentially Misidentifed Species - Northern Watermilfoil (M. sibricum) is native to both North America and Asia), and very similar to M. spicatum in morphology. Reexamination of the two species by Aiken et al. (1979) shows that they are distinct. M. sibiricum's range extends south to Chesapeake Bay. Herbarium specimens collected in Chesapeake waters between the 1880's and 1942 and identified as M. spicatum were actually M. sibricum (Couch and Nelson 1985). Because of the difficulty of separating the two species, the pre-M. spicatum range and the present occurrence of M. sibiricum, in Chesapeake Bay is unknown. M. verticillatum, somewhat more distinct, has been reported from Baltimore and ponds on the Eastern Shore (Sollers 1888; Tatnall 1946). Myriophyllum aquaticum (=M. brasilense, Parrot's Feather), also introduced in the Chesapeake Bay region, has emergent stems and leaves (Couch and Nelson 1991).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Plantae | Magnoliophyta | Magnoliopsida | Haloragales | Haloragaceae | Myriophyllum |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1942 | Established | Expanding | Introduced | Regular Resident | Europe | Eurasia | Ornamental(Aquatic Plant) |
History of Spread
The native and introduced ranges of Myriophyllum spicatum (Eurasian Watermilfoil) are somewhat obscured by confusion with M. sibericum (= M. exalbescens, Northern, Siberian or American Watermilfoil), which appears to be native to both Eurasia and North America. Nonetheless, M. spicatum is clearly an Old World species introduced to North America (Couch and Nelson 1991). It was probably imported as an ornamental plant by government workers (Couch and Nelson 1985; Couch and Nelson 1991).
Early records of 'M. spicatum' from the Chesapeake Bay, specimens from the Potomac (Ward 1881; cited by Reed 1977), Baltimore (Sollers 1888), and the Gunpowder River (1895; 1902) (United States Army Corps of Engineers 1977), have been re-identified as the native M. sibiricum (Couch and Nelson 1985; Couch and Nelson 1991). Seeds in sediment at Furnace Bay and Susquehanna Flats (date estimated as 1930's; Davis 1985) could be either species. There is a puzzling report of a watermilfoil outbreak in the 1930's in MD waters (United States Army Corps of Engineers 1977), but the identity of these plants is not clear.
The first verified record of M. spicatum was a collection from Belch Springs Pond, in Washinton DC in 1942. This plant spread rapidly in the northeast United States in 1940's and 1950's. Separate introductions through the ornamental plant trade probably occurred occurred in Western states at this time (Couch and Nelson 1985; Couch and Nelson 1991). In all the invaded regions, M. spicatum was spread by aquarium and fishpond escapes, trailered boats, and possibly by birds. By 1987, it was present in 34 states and 3 provinces.
Many M. spicatum invasions in lakes and estuaries seem to follow a characteristic pattern: (1) rapid biomass increases, accompanied by decreases in native species. (2) declines ofM. spicatum attributed to disease and other causes, (3) recovery at lower biomasses, with apparent coexistence with native submerged plants (Smith and Barko 1990).
Some of the first major Northern American records are listed below:
AZ - Myriophyllum spicatum was collected in 1944-46 (Couch and Nelson 1985; Couch and Nelson 1991).
CA and San Francisco Bay - Myriophyllum spicatum was first collected in CA in 1948 (Couch and Nelson 1985; Couch and Nelson 1991), and reached the San Francisco Bay Delta by 1976 (Cohen and Carlton 1995).
Great Lakes - Myriophyllum spicatum was collected in OH near Lake Erie, in 1949 (Couch and Nelson 1985; Couch and Nelson 1991), and established populations in Lake Erie by 1952, and in Lake Michigan in 1965 (Mills et al. 1993).
FL - Myriophyllum spicatum was collected in FL in the 1960's (Couch and Nelson 1985; Couch and Nelson 1991) and reached Gulf of Mexico estuaries in the Tampa-Sarasota area by 1970 (Reed 1977).
TX - Myriophyllum spicatum was collected in TX in the 1940's-50's (Couch and Nelson 1985; Couch and Nelson 1991).
WA - Myriophyllum spicatum was collected in the 1960's (Couch and Nelson 1985; Couch and Nelson 1991).
NC, Currituck Sound-Back Bay- Myriophyllum spicatum was first collected in 1965, and covered 27,000 ha by 1966, but declined in 1977, and was virtually gone together with other submerged aquatic vegetation by 1994 (Carter and Rybicki 1994).
Hudson River- Myriophyllum spicatum was first collected in the tidal Hudson River in 1970 (Mills et al. 1997).
British Columbia- Myriophyllum spicatum invaded Interior lakes, including Okanagan Lake in the 1970s and declined by 1991 (Couch and Nelson 1991).
Myriophyllum spicatum has been introduced to New Zealand (Howard-Williams 1993), and possibly to Australia (native status there is unclear) (Cook 1985).
The first verifed record of M. spicatum in North America and the Chesapeake region was from Belch Springs Pond, Washington DC in 1942. Records of Myriophyllum (spicatum or sibiricum) are sporadic in Chesapeake Bay records to 1954. Then a dramatic increase occurred, peaking in 1961-1963, at 40,000 ha. of coverage. At this time, living or dying M. spicatum could be found in virtually all portions of the Bay. Decline of M. spicatum in the 1960's was ascribed to 'Lake Venice' and 'Northeast' disease syndromes (Bayley et al. 1968; Stevenson and Confer et al. 1978). Recovery of M. spicatum, together with that of other submerged aquatic vegetation species. occurred in the 80's (Carter et al. 1985; Batiuk et al. 1994).
Chesapeake Bay records are given by tributary :
Rappahannock River - Small colonies were noted here in the early 1960s, but presumably disappeared with the general submerged aquatic vegetation decline of the 1970s. Myriophyllum spicatum was not found in this river in 1985-1992 (Orth et al. 1993).
Potomac River - Early records from the Potomac (Ward 1881; cited by Reed 1977) were M. sibiricum (Couch and Nelson 1985; 1991). Presumed M. spicatum were collected in 1951-1952 (Reed 1977; Stevenson et al. 1978). Dense beds were reported in tributaries by 1959. In 1961, Myriophyllum spicatum extended from Washington to Herring Creek, near the mouth of the Potomac (Stevenson et al. 1978). By 1979-80, M. spicatum was reduced to low abundances in the oligo-and mesohaline portions of the river (Haramis and Carter 1983). In 1984-85, it was second in abundance to Hydrilla verticillata (Hydrilla). (Carter et al. 1984; Carter and Rybicki 1986). Its range in 1992 (Orth et al. 1993; Batiuk et al. 1992) was fairly similar to that reported by Carter et al. (1984). By 2004,M. spicatum had returned to mesohaline portions of the Potomac (Orth et a. 2004; Fofonoff, personal observation)
Upper Bay and Tributaries - Early records for Gunpowder River (1895) and Baltimore (no specific location; Sollers 1888) were re-identifed as M. sibiricum (Couch and Nelson 1985). Herbarium specimens of verified M. spicatum were collected on Susquehanna Flats in 1951-52 (Stevenson and Confer 1978). Extensive growths of M. spicatum appeared in the Gunpowder River in 1954. By 1958, M. spicatum was blocking navigation in places. Biomass peaked in 1961-63, with M. spicatum dominating submerged aquatic vegetation populations south to the Rhode and Choptank Rivers (Southwick and Pine 1975; Stevenson and Confer 1978). Decline of M. spicatum was first observed in Lake Venice, Annapolis, 1962, and Northeast River, 1964, and ascribed to 'Lake Venice' and 'Northeast' diseases (Bayley et al. 1968; Bean et al. 1973; Stevenson and Confer 1978), believed to be caused by infectious agents. These disease conditions spread throughout Upper Bay populations. In some areas, other species initially recolonized space vacated by M. spicatum, but the continuing decline in the 1970's was part of a general disappearance of submerged aquatic vegetation throughout the Upper Bay (Bayley et al. 1978; Southwick and Pine 1975; Stevenson and Confer 1978). Some resurgence has occurred but the present Upper Bay population consists of scattered patches over a much smaller area than the peak range (Batiuk et al. 1992; Orth et al. 1993). By 2000, M. spicatum was growing again in Muddy Creek, on the Rhode River. It was found in the South and Severn Rivers, on the western shore, and the Elk, Bohemia, Sassafra, and Chester Rivers on the upper Eastern shore (Orth et al. 2004).
Eastern Shore Tributaries - Myriophyllum spicatum was reported from the Choptank and Nanticoke Rivers in 1969 (Stevenson and Confer 1978), but was not found in recent surveys (Orth et al. 1993; Orth et a. 2004).
History References - Batiuk et al. 1992; Bayley et al. 1968; Bayley et al. 1978; Bean et al. 1973; Carter et al. 1984; Carter and Rybicki 1986; Carter and Rybicki 1994; Cook 1985; Couch and Nelson 1985; Couch and Nelson 1991; Davis 1985; Haramis and Carter 1983; Howard-Williams 1993; Mills et al. 1993; Mills et al.1997; Orth et al. 1993; Reed 1977; Smith and Barko 1990; Sollers 1888; Southwick and Pine 1975; Stevenson and Confer 1978; United States Army Corps of Engineers 1977; Ward 1881.
Invasion Comments
History of Spread - Couch and Nelson's work (1985-1991) has substantially revised the early history of M. spicatum in Chesapeake Bay. Important features of the 'old' version are given summarized here. The first record of M. spicatum in Chesapeake Bay was taken to be the report of Ward (1881) for the Potomac River near Alexandria. Dry ballast or some other shipping vector was thought to be the mode of introduction. An environmental change, possibly increased calcium or nutrient inputs, pH change, etc., was believed responsible for the rapid proliferation of M. spicatum in Chesapeake Bay in the 1950's (Reed 1977; Stevenson and Confer 1978; United States Army Corps of Engineers 1977).
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 0.0 | 35.0 | 15.0 | 35.0 |
| Salinity (‰) | 0.0 | 13.0 | 0.0 | 13.0 |
| Oxygen | hypoxic | |||
| pH | 5.4000000000 | 10.0000000000 | ||
| Salinity Range | fresh-meso |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 500.0 | 500.0 |
| Typical Adult Size (mm) | 1600.0 | 1600.0 |
| Maximum Adult Size (mm) | 7000.0 | 7000.0 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs | 2.0 | 2.0 |
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
Myriophyllum spicatum (Eurasian Watermilfoil) attained extremely high abundances and biomasses, in the 1950s and early 1960s soon after its first collection in the Chesapeake Bay region. Economic impacts of this species were probably greatest at this time, and declined as M. spicatum apparently succumbed to several disease syndromes. In recent years, the abundance and range of this plant appears to be increasing again (Batiuk et al. 1994; Bayley et al. 1968; Carter et al. 1985; Stevenson and Confer et al. 1978).
Aesthetic - Aesthetic consequences of the M. spicatum invasion include reduced visibility, large tangles of plants washed up on beaches, reduced circulation and stagnation in coves, bad smells, impaired swimming (United States Army Corps of Engineers 1977; Stevenson and Confer 1978).
Fisheries - Fisheries impacts of M. spicatum include: tangling of fishing gear, reduced O2, possible effects on predatory fishes (Engel 1985; United States Army Corps of Engineers), interference with oysters (reduced circulation, increased sedimentation, etc. Stevenson and Confer 1978). Moderate levels of M. spicatum can be regarded as beneficial in previously unvegetated areas, but careful observation and control may be required in fisheries management (Engel 1995). With an increasing focus on the restoration of submersed aquatic vegetation (SAV), as a means of restoring water quality and habitat, resource managers have come to see M. spicatum as beneficial, colonizing areas where native SAV has disapppeared (Batiuk et al. 1994; Engel 1995).
Industry - The primary effect of M. spicatum on industry, including power plants, seems to be clogging of water intakes (United States Army Corps of Engineers 1977).
Boating - At the height of its invasion in Chesapeake Bay, M. spicatum clogged navigation channels, fouling of propellers and motors.
Health - Myriophyllum spicatum caused problems with clogging of water intakes, and the decomposition of excess biomass in drinking-water reservoirs. Mosquitoes can breed in stagnant water over dense beds of this or other submerged vegetation. This was considered a problem during big M. spicatum outbreaks in the 1950s and 1960s (United States Army Corps of Enginers 1977).
By 1958, M. spicatum beds in the Potomac became dense enough to cause complaints about impaired navigation, and damage to fisheries and recreation. Spraying with herbicides (2,4D) started in the Potomac and Upper Bay in 1962 and mechanical cutting began in 1963 (Carter and Rybicki 1994; Rawls 1975; United States Army Corps of Engineers 1977). The decline of M. spicatum alleviated these problems in Chesapeake Bay by the early 70's. Currently, M. spicatum is abundant, but is not considered a problem (Carter and Rybicki 1995). Attitudes regarding M. spicatum seem to have changed greatly: from 'mildly annoying to verging on economic disaster' (Stevenson and Confer 1978), to including a map showing 'Distribution restoration targets' for M. spicatum, along with those for native species (Batiuk et al. (1992).
References - Carter and Rybicki 1995; Engel 1995; Rawls 1975; Stevenson and Confer 1978; United States Army Corps of Engineers 1977
Economic Impacts Outside of Chesapeake Bay
Myriophyllum spicatum (Eurasian Watermilfoil) invasions have had serious economic and ecological impacts in Currituck Sound, NC (Carter and Rybicki 1994), the Hudson River estuary (Mills et al. 1997), and many interior lakes across North America (Couch and Nelson 1991). The impacts of these invasions have been similar to those of the great Chesapeake M. spicatum outbreak of the 1950's and 1960's, including interference with boating, fishing, reduced dissolved oxygen, replacement of more preferable wildlife foods, interference with predatory fishes, etc. (Aiken et al. 1979; Carter and Rybicki 1994). Extensive control programs were instituted in many of these bodies of water, including mechanical cutting, manipulation of water levels (in reservoirs) and herbicides, with varying success (Aiken et al. 1979; Smith and Barko 1990).
However, after the peaks of these invasions, biomass declines are frequently seen, often accompanied by disease-like conditions, after which populations are usually more manageable, and more likely to coexist with native flora (Bayley et al. 1968; Smith and Barko 1990). Consequently, M. spicatum has been treated less like an unmitigated pest in recent years (e.g. Engel 1995' s article - 'Eurasian watermilfoil as a fisheries management tool'). Fisheries benefits include providing habitat as a refuge for fish and invertebate prey species, as well as juveniles of sport fishes, nutrient absorption, resulting in limitation of phytoplankton growth, etc., particularly in lakes where native plants may have been limited by turbidity or eutrophication. However, obtaining these benefits may require careful monitoring and selective control (Engel 1995).
References - Aiken et al. 1979; Bayley et al. 1968; Carter and Rybicki 1994; Couch and Nelson 1991; Engel 1995; Mills et al. 1993; Mills et al. 1997; Smith and Barko 1990
Ecological Impacts on Chesapeake Native Species
Myriophyllum spicatum (Eurasian Watermilfoil) attained extremely high abundances and biomasses, in the 1950s and early 1960s soon after its first collection in the Chesapeake Bay region. Ecological impacts of this species were probably greatest at this time, and declined as M. spicatum apparently succumbed to several disease syndromes. In recent years, the abundance and range of this plant appears to be increasing again (Batiuk et al. 1994; Bayley et al. 1968; Carter and Rybicki 1986; Stevenson and Confer et al. 1978).
Competition - Myriophyllum spicatum is not unusually productive compared to other submersed aquatic vegetation (SAV) species, and it does not have unique photosynthetic characteristics (Smith and Barko 1990). It adapts to low light by shedding leaves on its lower stems and increasing leaf biomass near the surface. Its competitive advantages include its ability to form a dense canopy at the surface, shading out other species,and its ability to maintain some biomass through the winter when most other species die back, so that M. spicatum has a head start in spring (Aiken et al. 1979; Smith and Barko 1990). Adverse effects on native SAV include shading and competition for space. A native plant, Vallisneria americana (Wild Celery), which has most of its biomass near the bottom has superior rates of photosynthesis under low-light conditions but M. spicatum was able to partially displace it through shading (Titus and Adams 1979). This species is listed as highly invasive in DE and VA (Delaware Natural Heritage Program 1998; Virginia Department of Conservation and Recreation 1999).
Habitat Change - Myriophyllum spicatum beds develop a very dense surface canopy which provides cover to a variety of organisms. However, in Lake Opincon, ON, fewer benthic invertebrates were found under M. spicatum patches and on leaves than in a mixed native community (Keast 1984). The M. spicatum canopies offer a refuge to smaller fishes and juveniles of predatory species. Moderate growths can increase stocks of sport-fishes by increasing prey densities, but dense growths may restrict open-water planctivorous prey species, as well as restricting the vision and movement of predators (Engel 1995). In Currituck Sound, NC, following the 1965 M. spicatum invasion of a diverse native plant community, overall biomass of fishes increased [dominated by Perca flavescens (Yellow Perch, catfishes, and smaller sunfishes). Dense growths can decompose rapidly, lowering dissolved oxygen. Effects on hydrodynamics include reduced circulation, increased sedimentation, etc., and interference with oysters (Stevenson and Confer 1978).
The chemical environment in sediments was altered in stands dominated by M. spicatum and/or Hydrilla verticillata (Hydrilla), compared to stands dominated by the native Vallisneria americana (Wild Celery) in the Susquehanna Flats (MD), in upper most Chesapeake Bay. In H. verticillata/M. spicatum patches, sediments were less oxidized, porewater inorganic PO4 concentrations were higher, and PO4/Fe ratios were lower than in V. americana patches. M. spicatum and H. verticillata's roots are relatively shallow compared to those of V. americana. These two exotic plants extract most of their nutrients from the water column, while V. americana obtains most of its nutrients from the sediments (Wigand et al. 1997). Consequently, species replacement has implications for nutrient cycling. However, native plants vary in growth form, and some could also have similar behavior to H. verticillata and M. spicatum with regard to roots and nutrient use.
Food/Prey - Myriphyllum spicatum also provides a food source for birds including Fulica americana (American Coot), and many species of ducks and geese. These species increased during the M. spicatum invasion in Currituck Sound (Wicker and Endres 1995). However; M. spicatum is regarded as inferior to most native plants as a waterfowl food, and overwintering waterfowl decreased during in the upper Bay at the height of the M. spicatum invasion (Stevenson and Confer 1978). Toetz (1997) used the stable isotope 13C to investigate the role of M. spicatum in the fish and invertebrate components of an OK reservoir, but found no evidence of direct consumption by insect larvae, crayfish, or fishes.
References - Aiken et al. 1979; Batiuk et al. 1994; Bayley et al. 1968; Borawa 1979; Carter and Rybicki 1986; Engel 1995; Keast 1984; Smith and Barko 1990; Stevenson and Confer 1978; Titus and Adams 1979;Toetz 1997; Wicker and Endres 1995; Wigand et al. 1997
Ecological Impacts on Other Chesapeake Non-Native Species
Myriophyllum spicatum (Eurasian Watermilfoil) attained extremely high abundances and biomasses, in the 1950s and early 1960s soon after its first collection in the Chesapeake Bay region. Ecological impacts of this species were probably greatest at this time, and declined as M. spicatum apparently succumbed to several disease syndromes. In recent years, the abundance and range of this plant appears to be increasing again (Batiuk et al. 1994; Bayley et al. 1968; Carter et al. 1985; Stevenson and Confer et al. 1978).
Competition - The introduced submerged aquatic vegetation (SAV) species Hydrilla verticillata (Hydrilla), Potamogeton crispus (Curly Pondweed), and Najas minor (Minor Naiad) are probably adversely affected by M. spicatum to some extent through shading and competition for space. Myriophyllum spicatum maintains some biomass through the winter, so it shades other species during their spring emergence. However, H. verticillata, in particular, is capable of growth at low light levels (Barko and Smart 1981), and so could be less affected by competition.
Habitat Change - In Currituck Sound, NC, following the 1965 M. spicatum invasion, Micropterus salmoides (Largemouth Bass) biomass decreased. Numbers of young of the year remained similar; but numbers of older bass decreased (Borawa et al. 1979) suggesting that predation was adversely affected. Uniform high densities of M. spicatum may restrict movement and vision of predatory fishes, but patches may improve bass populations by providing a refuge for prey species (Engel 1995).
Herbivory - Cyprinus carpio (Common Carp) eat and uproot M. spicatum, and also generate turbidity which adversely affects the plant (Stevenson and Confer 1978). Ctenopharynogodon idella (Grass Carp) fed on this plant also (Pierce 1983), but only after most other plant foods have been eliminated (McKnight and Hepp 1995). Toetz (1997) used the stable isotope 13 C to investigate the role of M. spicatum in the fish and invertebrate components of an OK reservoir, but found no evidence of direct consumption by fishes, including C. carpio.
References - Barko and Smart 1981; Batiuk et al. 1994; Bayley et al. 1968; Borawa et al. 1979; Carter and Rybicki 1986; Engel 1995; McKnight and Hepp 1995; Pierce 1983; Stevenson and Confer 1978; Toetz 1997
References
Aiken, S. G.; Newroth, P. R.; Wile, I. (1979) The biology of Canadian weeds. 34. Myriophyllum spicatum L., Canadian Journal of Plant Science 59: 210-215Anderson, Richard D.; Brown, Russell, G.; Rappleye, Robert D. (1968) Water quality and plant distribution along the upper Patuxent River, Maryland, Chesapeake Science 9: 145-156
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: 219-235
Batiuk, Richard A.; Orth, Robert J.; Moore, Kenneth A.; Dennison, William C.; Stevenson, J. Court; Staver, Lorie W.; Carter, Virginia; Rybicki, Nancy (1992) Chesapeake Bay submerged aquatic vegetation, habitat requirements and restoration targets: a technical synthesis, In: (Eds.) . , Annapolis, MD. Pp.
Bayley, Suzanne; Rabin, Harvey; Southwick, Charles (1968) Recent decline in the distribution and abundance of Eurasian Milfoil in Chesapeake Bay, Chesapeake Science :
Bayley, Suzanne; Stotts, Vernon D.; Springer, Paul F.; Steenis, John (1978) Changes in submerged aquatic macrophyte populations at the head of Chesapeake Bay, 1958-1975, Estuaries 1: 73-84
Bean, George A.; Fusco, Michael; Klarman, William J. (1973) Studies on the "Lake Venice disease" of Eurasian Milfoil in the Chesapeake Bay., Chesapeake Science 14: 279-280.
Borawa, J. C.; Mullis, A. W.; Kerby, J. H.; Huish, M. T. (1978) Comparison of fish population data collected from Currituck Sound, North Carolina, before and after infestation by Eurasian watermilfoil, Journal of the Elisha Mitchell Scientific Society : 111
Borawa, James C.; Kerby, J. Howard; Huish, Melvin T., Mullis, Anthony W. (1978) Currituck Sound fish populations before and after infestation with Eurasian water-milfoil, Proceedings of the Annual Conference of the Southeast Association of Fish and Wildlife Agencies 32: 520-528
Brown, Melvin L.; Brown, Russell G. (1984) Herbaceous Plants of Maryland, , College Park. Pp.
Carter, Virginia; Gammon, Patricia T.; Bartow, Nancy C. (1984) Submersed aquatic plants of the tidal Potomac River, Geological Survey Bulletin 1543: 1-58
Carter, Virginia; Rybicki, N. B. (1994) Invasions and declines of submersed macrophytes in the tidal Potomac River and estuary, the Currituck Sound-Back Bay system, and the Pamlico River estuary, Lake and Reservoir Management 10: 39-48
Carter, Virginia; Rybicki, Nancy (1986) Resurgence of submersed aquatic macrophytes in the tidal Potomac River, Maryland, Virginia, and the District of Columbia, Estuaries 9: 368-375
Cook, C. D. K. (1990) Origin, autoecology, and spread of some of the world's most troublesome aquatic weeds, In: Pieterse, A. H. and Murphy, K. J.(Eds.) Aquatic Weeds: The Ecology and Management of Nuisance Aquatic Vegetation. , Oxford. Pp. 31-38
Couch, Richard; Nelson, Edward (1985) Myriophyllum spicatum in North America, In: (Eds.) First International Symposium on Watermilfoil (Myriophyllum spicatum) and Related Haloragaceae Species. , Vicksburg, Missisippi. Pp. 8-18
Couch, Richard; Nelson, Edward (1991) The exotic Myriophyllums of North America, In: (Eds.) A National Conference on Enhancing the States' Lake Management Programs. , Chicago, Illinois. Pp. 5-11
Creed, Robert P.; Sheldon, Sallie P. (1993) The effect of feeding by a North American weevil, Euhrychiopisis lecontei, on Eurasian watermilfoil (Myriophyllum spicatum), Aquatic Botany 45: 245-256
Davis, F. W. (1985) Historical changes in submerged macrophyte communities of Upper Chesapeake Bay, Ecology 66: 981-993
1998 Non-native plant species in Delaware. http://www.dnrec.statede.us/iw/weeds.htm
Engel, Sandy (1995) Eurasian watermilfoil as a fishery management tool, Fisheries 20: 20-27
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
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
Howard-Williams, Clive (1993) Processes of aquatic weed invasions: the New Zealand example, Journal of Aquatic Plant Management 31: 17-23
Hurley, Linda M. (1990) Field guide to the submersed aquatic vegetation of Chesapeake Bay., , Annapolis, MD. Pp.
Krauss, R.W.; Brown, R. G.; Rappleye, R. D.; Owens, A. B.; Shearer, C.; Hsiao, E.; Reveal, J. (1971) Checklist of plant species occurring within the hightide limits of the Chesapeake Bay, and its tributaries., , College Park, Maryland. Pp.
McKnight, S. Keith; Hepp, Gary R. (1995) Potential effect of grass carp herbivory on waterfowl foods, journal of Wildlife Management 59: 720-727
Mills, Edward L.; Leach, Joseph H.; Carlton, James T.; Secor, Carol L. (1993) Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions., Journal of Great Lakes Research 19: 1-54
Mills, Edward L.; Scheuerell, Mark D.; Carlton, James T.; Strayer, David (1997) Biological invasions in the Hudson River: an inventory and historical analysis., New York State Museum Circular 57: 1-51
1997-2024 USDA PLANTS Database.. Onine databse
Orth, Robert J.; Moore, Kenneth A. (1984) Distribution and abundance of submersed vegetation in Chesapeake Bay: an historical perspective, Estuaries 7: 531-540
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.
Pierce, Barry A. (1983) Grass carp status in the United States: a review, Environmental Management 7: 151-160
Rawls, Charles K. (1975) Mechanical control of Eurasian watermilfoil in Maryland with and without 2,4-D application, Chesapeake Science 16: 266-281
Reed, Clyde F. (1977) History and distribution of Eurasian watermilfoil in United States and Canada, Phytologia 36: 417-436
Smith, Craig S.; Barko, J. W. (1990) Ecology of Eurasian Watermilfoil, Journal of Aquatic Plant Management 28: 55-64
Sollers, Basil (1888) Check list of plants compiled for the vicinity of Baltimore., , Baltimore. Pp.
Southwick, Charles H.; Pine, Frank W. (1975) Abundance of submerged vascular vegetation in the Rhode river from 1966 to 1973, Chesapeake Science 16: 147-151
Stevenson, J. Court, Staver, Lorie W., Staver, Kenneth W. (1993) Water quality associated with survival of submersed aquatic vegetation along an estuarine gradient, Estuaries 16: 346-361
Stevenson, J. Court; Confer, Nedra M. (1978) Summary of available information on Chesapeake Bay submersed vegetation, , Annapolis MD. Pp.
Strong, Mark T.; Kelloff, Carol L. (1994) Intertidal vascular plants of Brent Marsh, Potomac River, Stafford County, Virginia, Castanea 59: 354-366
Tatnall, Robert R. (1946) Flora of Delaware and the Eastern Shore, , Wilmington. Pp.
Titus, John E.; Adams, Michael S. (1979) Coexistance and the comparative light relations of the submersed macrophytes Myriophyllum spicatum L. and Vallisneria americana Michx., American Midland Naturalist 102: 263-272
Toetz, Dale (1997) Does Eurasian watermilfoil, Myriophyllum spicatum, contribute to the diet of animals in a turbid reservoir?, Journal of Freshwater Ecology 12: 545-551
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
Ward, L. F. (1881) Guide to the flora of Washington and Vicinity, United States National Museum Bulletin 22: 1-264
Wicker, Anton M; Endres, Keith M (1995) Relationship between waterfowl and American coot abundance with submersed macrophytic vegetation in Currituck Sound, North Carolina., Estuaries 18: 428-431
Wigand, Cathleen; Stevenson, J. Court; Cornwell, Jeffry C. (1997) Effects of different submersed macrophytes on sediment biogeochemistry, Aquatic Botany 56: 233-244