Introduction
Lake Guntersville is Alabama’s largest reservoir at 69,000 acres and is famed as one of the best bass fishing lakes in the country. In addition to world class fishing it is also a popular destination for recreational boaters, water skiers, and campers. The great fishing success at Lake Guntersville can be attributed, at least in part, to the vast expanses of aquatic plants that occupy the lake. Aquatic plants provide many important ecological benefits; such as, improving water clarity, stabilizing sediments, providing fish habitat, and adding to the overall ecological diversity in shallow littoral areas. In the past few decades, invasive non-indigenous aquatic plant species such as Eurasian watermilfoil and hydrilla have become well established throughout Guntersville. Long growing seasons and warm temperatures, combined with the rapid growth of these species, have allowed them to flourish throughout the lake and reach nuisance levels that can negatively impact a water body. Impacts include, alterations in the interactions between fish and other aquatic species, constricting navigation canals, declines in recreational use, lowering property values, disrupting nutrient cycling, and provide mosquito breeding habitat. In addition to the aforementioned aquatic plants, Lake Guntersville also harbors a number of native aquatic plant species. Floating plants such as white water lily and American lotus; emergent plants such as water primrose and water willow; and a large number of submersed plants such as eel grass, coontail, southern naiad, and several pondweeds, to mention a few.
The dramatic increase in coverage of Eurasian watermilfoil and hydrilla has caused concerns from homeowners, recreational lake users, and commercial businesses. Eurasian watermilfoil was at one time the dominant species in the lake occupying an estimated 15,000 acres in the late 80’s, but in the past 10 years hydrilla has taken that position. Hydrilla is a very versatile plant species and can grow in both static and flowing water, from several centimeters to 45 feet in depth in some parts of the country. It has been found in up to 20 feet of water in the Guntersville Reservoir. Due to its growth and reproduction habits hydrilla has been referred to as “the perfect aquatic weed”. Hydrilla occupied an estimated 400 acres in 1996 which increased 10 fold to an estimated 4000 acres in 1998. Recently, in 2012, hydrilla was estimated to occupy 10,000 acres with milfoil occupying another 8,000. Together these plants infest 18,000 acres and nearly 80 percent of developed shorelines.
In addition to Eurasian watermilfoil and hydrilla, several other non-native plant species occupy Lake Guntersville. Emergent and floating plants alligatorweed and water hyacinth can also be found in the Tennessee Valley Reservoir systems. Alligatorweed is typically found in the backs of creeks, but it is not uncommon to see plant mats floating down the river. Cuban bulrush and water hyacinth are not frequently seen on Lake Guntersville, but are known to occur in other Tennessee River lakes. Other problematic species that have not found their way into Guntersville include giant salvinia and floating crested heart. Both of these species are very aggressive and can become very problematic. It is in our best interest as a stakeholder group to properly manage the aquatic plants and to meet the needs of all interest groups that utilize Lake Guntersville.
References
Gettys, L.A, Haller, W.T., and Bellaud, M. (eds). Aquatic Ecosystem Restoration Foundation (AERF) 2009. Best Management Practices Handbook: Biology and Control of Aquatic Plants.
Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), “The perfect aquatic weed”. Castanea 61: 293-304.
Madsen, J.D. 2004. Invasive aquatic plants: A threat to Mississippi water resources. Pages 122-134 in 2004 Proceedings, Mississippi Water Resources Conference.
Pimentel, D., L. Lach. R. Zuniga, and D. Morrison. 1999. Environment and Economic Costs Associated with Non-Indigenous Species in the United States. Ithaca, New York: College of Agriculture and Life Sciences, Cornell University.
Webb, D. Personal Communication. July 10, 2014.
Yeo, R.R., R.H. Falk, and J.R. Thurston. 1984. The morphology of hydrilla (Hydrilla verticillata (L.F.) Royle). J. Aquat. Plant Manage. 22: 1-17.
Hydrilla
(Hydrilla Verticillata L.f Royle)
Introduction
Hydrilla, a native plant of Asia, was first introduced to the United States in Florida in 1960. Since its introduction it has spread rapidly throughout the United States. Hydrilla’s ability to survive well in freshwater reservoirs and rivers has allowed it to become problematic. Reduced water flow, associated with clogged irrigation and/or water control structures, interferences with navigation, boating, swimming, and fishing are some of the negative impacts caused by extensive hydrilla growth. Hydrilla populations have also been known to outcompete and displace native aquatic plants, such as pondweeds (Potamogeton spp.). The dense plant canopy produced in an established hydrilla bed makes it difficult for other aquatic plants to flourish.
Description
Hydrilla is a submersed plant that grows in a variety of water conditions. It is a very versatile plant species and can grow in both static and flowing water, from a few centimeters to 15 meters (m) in depth. The depth at which hydrilla can become established is often dependent on water turbidity, although it is a shade tolerant species. Hydrilla can be found in a variety of water chemistry situations and due to its growth and reproduction habits hydrilla has been referred to as “the perfect aquatic weed”. Both dioecious and monoecious types are present in the Tennessee Valley. Stems are ascending towards the water surface and often branch out when they reach the water surface. Leaves are sessile occur in whorls, mostly 4-8 leaves per whorl. Leaves are typically 1.5 cm in length, oblong, and have serrate leaf margins. Flowers are very small and rise from the leaf axils.
Regulation
Hydrilla is listed as a federal noxious weed.
Distribution
Hydrilla is found throughout the United States from Maine down the east coast to Florida. It is also found throughout the Midsouth from Georgia to Texas and north to Indiana. It has also been documented in Washington, California, and Arizona on the west coast. It is currently present in the Tennessee Valley Reservoir System.
References
Godfrey R.K. and J.W. Wooten. 1979. Aquatic and Wetland Plants of Southeastern United States Monocotyledons. pp 76.
Haller, W.T. and D.L. Sutton. 1975. Community structure and competition between hydrilla and vallisneria. Hyacinth Control J. 13: 48-50.
Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), “The perfect aquatic weed”. Castanea 61: 293-304.
Netherland, M.D. 1997. Turion ecology of hydrilla. J. Aquat. Plant Manage. 35: 1-10.
Yeo, R.R., R.H. Falk, and J.R. Thurston. 1984. The morphology of hydrilla (Hydrilla verticillata (L.F.) Royle). J. Aquat. Plant Manage. 22: 1-17.
United States Dept. Agriculture Natural Resources Conservation Service Plants Database. June 16th, 2014. https://plants.usda.gov/java/reference?symbol=HYVE3.
Eurasian Watermilfoil
(Myriophyllum Spicatum L.)
Introduction
Eurasian watermilfoil is a submersed plant that was introduced in several locations in the United States from Europe in the 1940’s. It has the ability to form dense mats within infested areas. These dense mats often shade out desired native species, alter macro invertebrate communities, and may interfere with fish spawning in shallow areas. Invasion and explosive growth of Eurasian watermilfoil can displace native plants and reduce species diversity within the invaded area.
Description
Eurasian watermilfoil is a submersed perennial aquatic plant that most often occurs in waters 1-4 meters deep. Leaves are whorled around a glabrous stem. Leaves are typically 1.5-4.0 cm long and occur in 4 leaves per whorl. The leaves are highly divided “feather like” and consist of 14-24 pairs. Inflorescences is a terminal spike (5-20 cm). Flowers are formed on short aerial stems that contain both pollen bearing “male” and seed producing “female” flowers.
Regulation
Eurasian watermilfoil is not listed as a federal noxious weed
Distribution
Eurasian watermilfoil is found throughout the United States and North America. It has been documented from Florida to Quebec in the east, across the central US, and from California to Alaska in the west. It is currently found in the Tennessee Valley Reservoir Systems.
Reproduction
Eurasian watermilfoil is capable of reproducing sexually and asexually, with asexual reproduction being the most important. Small buds can form on root crowns and detach at the end of winter allowing new plants to be established early in the spring. During peak growing season stems can release numerous fragments (10-20 cm) either naturally or by plants being broken by wave action or human activities. These fragments are often viable and allow new plants to become established in new areas.
References
Aiken, S.G., P.R. Newroth, and I. Wile. 1979. The biology of Canadian weeds. 34. Myriophyllum spicatum. L. Can. J. Plant Sci. 59:201-215.
Newroth, P.R. 1985. A review of Eurasian Water milfoil impacts and management in British Columbia pp. 139-153. In: Proc. First Int. Symp. On watermilfoil (Myriophyllum spicatum) and related Holoragaceae species July 23-24, 1985. Vancouver, BC, Canada. Aquatic Plant Management Society, Inc.
Smith, C.S. and J.W. Barko. 1990. Ecology of Eurasia watermilfoil. J. Aquat. Plant Manage. 28:55-64.
Madsen, J.D. 2009. Eurasian Watermilfoil. In: Biology and Control of Aquatic Plants: A Best Management Practices Handbook. (eds) Gettys, L.A., Haller, W.T., and Bellaud, M. pp.95-97.
