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Aquatic Invasive Species What are aquatic invasive species?
What are aquatic invasive species? The following is one of many different definitions: "a non-native species introduced to an aquatic ecosystem that causes environmental and/or economic harm." Other terms such as "exotic species" and "nuisance species" are uses interchangeably with invasive species. Regardless of the exact definition or terminology, aquatic invasive species have come to the forefront of issues impacting our lakes, streams, and wetlands and are increasingly the focus of Watershed Council monitoring and management programs.
What are the impacts of aquatic invasive species? There are both economic and ecological impacts, both of which are quite serious. Economically, there are losses in tourism, sports-fisheries, industry and more. In Michigan, fishing expenditures alone exceed $800,000,000 per year1, a figure that could drop substantially as aquatic invasive species disrupt ecosystems and impact fisheries. Losses in the U.S. are estimated at $78.5 billion annually and studies have estimated lost property values on infested water bodies of up to $12,000 per property2. Ecologically, aquatic invasive species impacts include food-web disruptions, native species reduction or loss (and dependent species), water quality degradation, and the introduction of pathogens. Furthermore, ecosystem disruptions and imbalances can result in increased danger to human health.
How are we dealing with aquatic invasive species in northern Michigan? The Watershed Council works on many fronts when it comes to invasive species. We have programs to monitor the spread of invasive species, such as the Aquatic Invasive Species Patrol, which is described in more detail below. We also actively work to manage invasive species in our lakes and streams where it is feasible. We have worked with several lake associations throughout northern Michigan to control Eurasian watermilfoil and purple loosestrife infestations. Beyond monitoring and management, the Watershed Council works to combat the aquatic invasive species problem on the policy front; encouraging and supporting legislation that addresses the spread of invasive species. 1 U.S. Department of the Interior, Fish and Wildlife Service and U.S. Department of Commerce, U.S. Census Bureau. 2001 National Survey of Fishing, Hunting, and Wildlife-Associated Recreation. Invasive Species Descriptions Purple loosestrife (Lythrum salicaria)
Native to Europe and Asia, purple loosestrife can be identified by its purple flowers which bloom from June to September. Purple loosestrife produces square woody stalks 4 to 7 feet high. Leaves are heart or lance shaped and flowers have 5 to 7 petals. Due to the long flowering season, purple loosestrife plants have the ability to produce millions of seeds each year. In addition to seeds, purple loosestrife can also produce vegetatively by sending up shoots from the root systems. The underground stems can grow up to a foot each growing season. Purple loosestrife threatens native species by crowding them out and competing for water and sunlight. When loosestrife replaces native plants, it destroys the habitats of animals and insects that depend on native species for food and shelter. Duck, geese and muskrat populations have all seen declines since purple loosestrife was imported. Dense stands of loosestrife impede water flow and impair the use of wetland recreation areas, in turn requiring costly management efforts. For years, conventional ways of dealing with the purple loosestrife problem were tested. For small stands of loosestrife, burning, spraying, and pulling are still the best ways to rid an area of the plants. However, for large stands, such methods are impractical and costly.
Luckily, scientists have found an alternative-biological control offers a natural solution. By introducing a natural predator of purple loosestrife from its native range, wetland protectors have been able to significantly reduce the density of purple loosestrife populations. The Galerucella beetle, which keeps plant populations in check in Europe and Asia, feeds on the stem, leaf, and bud of loosestrife plants, preventing the plant from reproducing. Galerucella beetles have been released in 16 states to date according to the National Parks Service and the Michigan Sea Grant reported successful depletion of purple loosestrife in Michigan, Ontario, and Minnesota by using Galerucella beetles. Rearing and releasing Galerucella beetles is simple, though rather labor intensive. School and environmental groups have been pivotal in Michigan's Galerucella release programs. Tip of the Mitt Watershed Council has played an active role in fighting purple loosestrife in Northern Michigan by organizing groups to collect and release Galerucella beetles. Zebra mussels (Dreissena polymorpha)
The sheer number of zebra mussels in combination with their feeding habits has caused severe disruptions in aquatic ecosystems. Each zebra mussel is capable of filtering a liter of water per day; thus, removing almost every microscopic aquatic plant and animal (phytoplankton and zooplankton). This ecosystem disruption impacts aquatic organisms throughout the food chain, from tiny crustaceans to large trout. The effect of their feeding habits is easily discernable in water transparency data collected by volunteers, which shows that water has become clearer in lakes infested with the mussels. Increased water clarity has lead to yet another impact from zebra mussels; sunlight penetrates to greater depths and results in increased growth of rooted aquatic vegetation and bottom-dwelling algae. While they continue to filter phytoplankton and zooplankton, they also filter other substances known as toxic contaminants. Zebra mussels have high levels of body-fat-thus, allowing them to accumulate ten times more PCBs and other toxic contaminants than the native mussels. Once these contaminants are stored in their bodies, they are then transferred up the food chain to their predators. Predators include some species of ducks, freshwater drum, carp, and lake sturgeon. Eurasian watermilfoil (Myriophyllum spicatum) As Eurasian watermilfoil takes hold in a lake, it causes problems for the ecosystem and for recreation. It tolerates lower temperatures and starts earlier than other aquatic plants, quickly forming thick underwater stands of tangled stems and vast mats of vegetation at water's surface. These dense weed beds at the surface can impede navigation - and no one likes to swim in areas thick with aquatic plants. The lake ecosystem suffers because Eurasian watermilfoil displaces and reduces native aquatic plant diversity, which is needed for a healthy fishery. Infestations can also impair water quality due to dissolved oxygen depletion as thick stands die and decay. A key factor in the plant's success is its ability to reproduce through both stem fragmentation and underground runners. Eurasian watermilfoil spreads to other areas of a water body by fragmentation. A single stem fragment can take root and form a new colony. Locally, it spreads by spreading shoots underground.
Boat traffic is responsible for the majority of introductions into new water bodies and for spreading the plant within a water body. Watermilfoils commonly become entangled in boat propellers, attach to keels and rudders of sailboats, and get caught up in boat trailers. Stems that become lodged in watercraft and trailers are transported to other water bodies, which is all that is needed to colonize new water bodies. Boats also contribute to natural seasonal fragmentation and the distribution of fragments throughout infested lakes. Eurasian watermilfoil has difficulty becoming established in lakes with well established populations of native plants. In some lakes, the plant appears to coexist with native flora and has little impact on fish and other aquatic animals. Removing native vegetation, whether physically or with herbicides, creates the perfect opportunity for invading Eurasian watermilfoil. Identifying Eurasian watermilfoil can be tricky since it looks similar to native watermilfoils. Native watermilfoils usually have less than 12-14 leaflets on one side of the leaf, whereas Eurasian watermilfoil has more than 12-14 leaflets. The Eurasian leaf is conspicuous in that it appears to have a "clipped" end and somewhat of a "fish bone" appearance. Floral features also help distinguish species; floral bracts being longer in native milfoils and the flowering top of the Eurasian typically has a reddish hue.
There are several techniques used to control nuisance aquatic plants, but most are not effective or practical for Eurasian watermilfoil. Manual or mechanical removal can exacerbate the situation because of the plants ability to colonize through fragmentation. Benthic barriers, placed over the plants, have been installed in Higgins Lake with fairly good results. Herbicides may be suitable for spot application, but are not recommended for large infestations due to ecosystem-wide impacts and uncertainties regarding the impacts of chemicals on non-target aquatic organisms and humans. Biological control using a native weevil is the safest ways to control Eurasian watermilfoil, but can be costly depending on the degree of infestation and effectiveness of treatment. Ultimately, prevention is the most effective and least expensive strategy for controlling Eurasian watermilfoil, as well as all other invasives. Aquatic Invasive Species Patrol The Aquatic Invasives Species Patrol project trains volunteers to identify and inventory aquatic invasive species. The first set of "train the trainer" workshops was held during the summer of 2006. Workshop participants learned to identify purple loosestrife, Eurasian watermilfoil, and round goby; management options for each species; and inventory methods to record the location of these species in our service area. The participants of these workshops will train others to perform identification and inventories. Start up funding for this project was provided by the MDEQ Aquatic Invasive Species Small Grants Program. Using this data the Watershed Council has developed a database and locator maps to track the spread of invasive species, identify areas that are free from invasives, and determine management options for specific locations of aquatic invasive species. The database and maps will be updated regularly as data is collected by staff and volunteers. Aquatic Invasive Species Patrol database Aquatic Invasive Species Patrol locator maps If you would like to report a location to be added to the database, download and print the Aquatic Invasive Species Locator Data Sheet. Please return the data sheet to the address indicated on the form. Aquatic Invasive Species Locator Data Sheet Volunteer Purple Corps The Volunteer Purple Corps project was initiated summer of 2006 to build upon the work of the Michigan State University Purple Loosestrife Project. For this pilot project, volunteers from Pickerel-Crooked Lakes Association and Burt Lake Preservation Association worked through the summer to perform a detailed inventory of purple loosestrife in their watersheds. This data will be utilized in the Aquatic Invasive Species Patrol database, and will aid the Watershed Council in prioritizing locations for management and developing a purple loosestrife management plan. This project serves as a pilot for the development and implementation of additional purple loosestrife management plans for the rest of our service area. This project was funded through a grant from the Michigan Nongame Wildlife Fund and citizen contributions to the fund. Volunteer Purple Corps pilot project area Purple Loosestrife Locator Datasheet 426 Bay Street Petoskey, Michigan 49770 Phone: (231) 347-1181 |
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