Lakes And Aquatic Plants

Property owners with lakes, ponds, or other aquatic or wetland habitats have a number of concerns not usually faced by other landowners, such as erosion, water quality, and algae blooms. In addition, many of the plants growing in these areas are unique to aquatic settings, and a few of them are non-native problem species that should be controlled.

1. Lake Aging
Lake aging is a slow, natural process whereby lakes collect nutrients and sediments from in-flowing waters. With time, algae levels increase, and water visibility and depth decreases. Eventually, most lakes will become sufficiently shallow to form wetlands.

Human activities can greatly accelerate the natural process of lake aging by causing a rapid influx of nutrients and sediments. Common sources of these nutrients and sediments are stormwater runoff from developed areas, failing septic systems, overuse of fertilizers, logging, and improperly-managed construction activities and agricultural practices. The influx of nutrients can produce explosive algae population growths, called blooms, resulting in reduced water quality and unpleasant, smelly scums. It can also lead to an overabundance of aquatic plants, which can degrade fish habitat, limit human recreational uses, and deplete the oxygen supply in the water.

2. Aquatic Plant Benefits
Regardless of the age of the lake or pond, aquatic plants serve many important functions. These include:

Stabilizing shorelines:
The roots of many aquatic plants, particularly emergent plants (those growing in standing water with much of their growth above the water), reinforce shorelines and protect soil against erosion from wind and wave action, boating wakes, currents, and other forces.

Providing habitat:
Many aquatic plants provide cover, food, nesting sites, and resting areas for fish, amphibians, invertebrates, birds, and mammals. Settings with a diversity of native aquatic plants will attract a variety of native animal species.

Resisting invasion by non-native plants:
A healthy native aquatic plant community will resist the establishment of invasive non-native plants, and often prevent them from becoming a serious problem.

Reducing nutrients:
Aquatic plants tend to bind up nutrients, leaving less available for algae and making algae blooms less likely. Emergent plants also slow water movement along shorelines, causing nutrient- laden sediment to settle to the bottom, where it is less available to algae.

Providing shade:
Aquatic plants, particularly those with floating leaves, create shade below their leaves. This restricts algal growth to open areas where light is available. The shade also reduces water temperature, which allows more oxygen to dissolve in the water, making the water more hospitable to animals that use dissolved oxygen (such as fish).

Producing oxygen:
As a by-product of photosynthesis, aquatic plants release oxygen into the water. This is important to fish and other aquatic organisms that depend on dissolved oxygen to survive.

Persons interested in planting native plants in or around lakes, ponds, streams, or other aquatic or wetland habitats should consult the sections on Emergent Plants and Submergent & Floating-leaved Plants in Appendix C, and Problem Aquatic and Terrestrial Plants (Appendix B). These sections will help you identify which species are appropriate for your setting, and prevent planting problem species.

Although some native aquatic plants can be purchased at nurseries, often the only way to obtain them is to propagate them from plants growing in your area. Species-specific propagation instructions can be found in Appendix C. However, before you start collecting seeds, plants, or cuttings, review the guidelines listed on page 9 (plant collecting ethics).

Because many aquatic plants are difficult to identify, be sure to take samples of the plants you intend to use to an aquatic plant specialist for identification before you plant them: otherwise, you may end up introducing a noxious weed or problem plant to your property. For help identifying aquatic plants and determining which plants are appropriate for your lake, contact your county WSU Extension–WSU agent, local university staff familiar with aquatic plants, or one of numbers listed below for the Washington State Department of Ecology.

3. Aquatic Plant Management
While many landowners are interested in establishing native aquatic plant communities in and around their lakes or ponds, some property owners may be more concerned with controlling aquatic plants, particularly if the plants are non- native or are creating problems.

Aquatic plant management should take into account all of a lake's users. Not only are lakes important to people for reasons ranging from aesthetics to recreation, but there are other lake dwellers to consider: fish, amphibians, and other aquatic organisms, plus the birds and other wildlife that depend on a healthy lake. In addition, downstream residents and resources are impacted by the quality and quantity of water flowing out of the lake.

The most effective long-term control of problem aquatic plants will include efforts to control the sediments and nutrients entering the lake. Certain practices should be encouraged, including landscaping with native vegetation to reduce and filter runoff, and properly maintaining septic systems to prevent nutrient-rich effluent from leaching into the lake. Contaminants such as used motor oil, car washing detergents, and soil from landscaping projects should be kept out of stormwater draining into the lake. Fertilizers and pesticides should be kept out of the lake by planting native vegetation and by using few or no garden chemicals.

Before you begin using any aquatic plant control technique, salvaging desired plants from a lake or wetland, or placing desired plants into a lake or wetland, consult with the Washington Department of Ecology and your county or city government. Many jurisdictions have regulations that limit or prohibit removing plants from or adding plants to wetlands or lakes. Because these regulations were designed to protect habitat and water quality, they usually have exceptions or allow one to obtain a permit for changes that will actually improve habitat and water quality. You will save yourself a lot of headaches (and possibly money) if you check first and get all of the required permits.

4. Contacts and Other Resources
Washington State Department of Ecology publishes the Citizen's Manual for Developing Integrated Aquatic Vegetation Management Plans. In addition, it administers the Aquatic Weed Management Fund, a grant program to assist in the management of aquatic weeds. Contact information is in the Appendix of the manual.

United States Environmental Protection Agency

Clean Lakes Program:
(206) 553-1571

Washington State Noxious Weed Control Board
(206) 872-2318 or 872-2972

Some counties also have specific agencies to assist you with the long-term planning necessary to address the complexities of aquatic plant management.

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