Invasive Aquatic Weeds Pose A Real Threat to Georgia Waterways

 Aquariums and water gardens are very popular with homeowners today. They provide aesthetic as well as educational additions to the home. There are many different types of animals and plants that can be utilized for these environments. However, many people are surprised to learn that some of these aquatic organisms used in aquariums and water gardens have been a source of invasive species in water ways. The popularity of these hobbies has led to the introduction of many aquatic invasive pests when people with dump aquarium water or release unwanted aquatic plants and animals into water ways. Sometimes people think that these beautiful plants would improve our ponds and lakes when they do not.

 Invasive species are increasingly becoming one of the most serious environmental problems facing us. Since these organisms are not native to a specific ecosystem, they have the potential to cause ecological and economic damage, and possibly even a threat to human health. All plants have natural growth checks, such as fungus, bacteria and ordinary plant diseases; fish and other animals; climate; geology, etc., that help keep their populations in balance. In short, this process is nature’s way of keeping everything in balance. In a balanced ecosystem, variety reigns and there is a biodiversity of plants, continually growing and evolving through time. When a plant or animal species that has evolved in a different ecosystem is introduced into a new area, it usually lacks natural controls to keep its population under control. Although not always the case with non-native species, it can grow rapidly, quickly covering and replacing the plants that were naturally there in the first place.

Invasive plants succeed at colonizing areas because they are adaptable to a wide range of soil and water acidity and nutrient levels, different water and air temperatures, salinity, changes in the level of water, and the amount of dissolved oxygen. They reproduce early and often in large numbers, both by seeds and vegetatively, are rapidly growing, and often are resistant to control methods. Aquatic species cost our nation billions of dollars every year. They damage waterways in several ways. They disrupt native vegetation growth, harm fish and other aquatic animals, and can also harm local economies by discouraging tourism and angling and by reducing property values. Several of the invasive aquatic weeds are on the federal noxious weed list meaning it is a violation of federal law to possess or sell them.

One such plant is the water hyacinth (Eichhornia crassipes), a native to South America, one of the worst of all of the aquatic weeds. It invades waterways and forms a dense floating mat of vegetation shading the underwater environment. This reduces light levels to plants and animals under water and also depletes oxygen levels. Water hyacinths are some of the fastest growing plants known. It doubles the area it covers in just two weeks. Each plants produces millions of seeds and it also reproduces vegetatively. Water hyacinths form large mats of floating weeds that can clog irrigation pipes, damage boats, push over small bridges, and can enhance mosquito breeding areas. In many parts of Georgia in recent years, some ignorant people have released this plant into the lakes and ponds, where their populations have exploded leading to very costly clean ups. A common myth says that the plant is unable to survive winter in the northern part of Georgia, but several populations of this plant has become well established in local waterways in spite of freezing temperatures.

Another harmful invasive aquatic weed is hydrilla (Hydrilla verticillata). It grows under water and can root at a depth of 20 feet. It forms a dense mat of tangled masses on the surface of water. As a child, my grandfather owned some property next to a lake in Liberty County, Ga. Over time, the lake became completely covered with this weed, and fishing and boating was next to impossible. First introduced as an aquarium plant 50 years ago, it has spread throughout the Southeast. It restricts native vegetation, irrigation, fishing, and hydroelectric facilities. It reproduces through root tubers and by fragments of the plant, not by seed, making it easily spread by boating equipment. Once the hydrilla forms tubers, which can lie in the sand and mud for many years, eradication is almost impossible. Hydrilla is controlled by using a combination of herbicides, cultural, and mechanical methods. Hydrilla is a federal noxious weed; any occurrence should be promptly reported.

Eurasian watermilfoil (Myriophyllum aquaticum), also called parrot feather, is a submerged/emergent plant invading aquatic habitats throughout the nation, and one of the most common aquatic weeds. It reproduces vegetatively by rhizomes and fragmented stems, and forms dense mats of vegetation on water surfaces. The plant is often spread by boats, trailers, and animals that move from one water body to another. Eurasian watermilfoil is native to South America, and was first introduced into the United States a century ago as an aquarium and aquatic garden plant. The plants are rooted to the bottom of the waterways with the stems growing to the surface. It grows best in water that is stagnant or slow moving, like ponds, lakes, and canals. It interferes with fish spawning habitats.

Giant salvinia (Salvinia molesta) is a free floating aquatic fern that growing in chains forming a dense, floating mat up to two feet thick. The leaf surfaces have rows of hairs that look like tiny eggbeaters. It can infest any type of water way, but prefers slow moving or stagnant waters. It can tolerate extreme heat and cold, but will not tolerate ice formation on the surface of the water body. The plant reproduces rapidly and can double its numbers in an infested area in as little as a week to ten days under the right conditions. Even small fragments of the plant can reproduce and infest an area. Researchers at the USDA Invasive Plant Lab in Ft. Lauderdale, Fla. have had some excellent results of using a biocontrol insect, a weevil (Cyrtobagous salviniae). It has been used in at least 13 nations to control giant salvinia. The weevil lives in the leaves or under the water in its rhizomes. The adult female chews in the leaf buds and then lays her eggs. The larvae hatch and begin eating the leaves and other parts of the plant. More experimentation and evaluation of this insect is necessary before wide spread use of it is initiated. Giant salvinia is a federal noxious weed; any occurrence should be promptly reported.

In addition to plants, there are several types of animals, particularly snails, often used in aquariums and water gardens, threatening water ways. The Channeled Apple Snail (Pomacea canaliculata), a native to South America, is invading many streams, rivers, lakes, and wetlands in the Southeastern United States. The snail consumes many types of vegetation, and threatens native snail species by altering habitats and competing with them for food sources. It reproduces rapidly and can lay several hundred eggs at one time. The Giant African Snail (Achatina fulica), is not considered an aquatic pest, but is invasive and can be very harmful. The adult snail can be up to eight inches in length. It can