Ponds Come in All Forms
Ponds have diverse physical and chemical features and thus no two are identical. Some are built for aesthetic or recreational uses, while others function primarily in storm-water management. Community retention ponds are designed to capture sediment and filter pollutants from storm-water runoff before returning it to our creeks, rivers, and lakes, which can result in an abundance of aquatic vegetation and algae. These ponds are specifically engineered to capture and release water slowly, which minimizes flooding and erosion within the community. In many cases, there is no consideration of the long-term appearance or water quality during the design process.
Pond management is the practice of maintaining a healthy balance between the function, appearance, and ecology of a pond. Some of which may be more important to the owner depending on the location and use of the pond. Common principles of pond management include water quality and sediment monitoring, fisheries management, and aeration enhancement. However, the biggest concerns of pond owners often pertain to aquatic weed and algae growth. Nuisance aquatic growth is a function of temperature, sunlight, water depth, and nutrient concentrations.
Ponds are NOT Swimming Pools!
A big misconception among pond owners is that their water should be extremely clear and free of all aquatic vegetation. The truth is that ponds should have a visibility of 18-24 inches and a noticeable green tint to the surface. This indicates a healthy phytoplankton bloom and good oxygen production. Furthermore, native aquatic vegetation should be preserved in moderation. The key word there is native; all invasive species should be completely controlled to prevent their spread to other bodies of water. Examples of desirable vegetation include native pondweed species and shoreline plants such as primrose, water willow, and spikerush. Common invasives include hydrilla, giant salvinia, and Eurasian watermilfoil.
Desirable Pondweed
The benefits of native aquatic vegetation are diverse. Aquatic plants uptake nutrients that would otherwise be used by harmful algae blooms. Shoreline aquatic plants stabilize soils and minimize bank erosion. Preserving aquatic vegetation in moderation is paramount when fish production is important to the pond owner. For example, submersed plants produce vital oxygen and create the ideal ecosystem for both gamefish and forage species. The lesson here is that eradication of all aquatic growth is not the answer to maintaining a healthy pond. It is recommended to tolerate some aquatic growth regardless of the type of pond or its intended use. A general rule of thumb is that native vegetation should be managed not to exceed 20-30% of the pond surface.
Aquatic Vegetation and Algae Can Become a Problem
Community storm-water ponds are essentially sediment basins that are saturated with phosphorus. This creates shallow, nutrient rich waters that are prone to severe outbreaks of algae and aquatic weeds. These ponds are the most challenging and often require persistent management to meet the expectations of the community.
Aquatic growth should be managed when it begins to interfere with the function, appearance, or ecology of the pond. Problems associated with excessive weed coverage include clogging fountains or submersible pumps, angling interference, and disruption of gamefish/forage balance. Aquatic weeds can block storm-water inflows and outflows which increases the risk of flooding. Uncontrolled submersed or floating weeds can lead to dissolved oxygen problems and potential fish kills. Most importantly, some species of algae referred to as harmful algae blooms (HAB’s) can affect pets and wildlife when left unchecked. Note that most species of algae are harmless and even beneficial to water quality!
Filamentous Algae Before and After Treatment
Chemicals are NOT the Only Option
Aquatic vegetation and algae control should be accomplished through an integrated pest management (IPM) plan that includes both preventative and reactive measures. This may include nutrient mitigation, biological controls, supplemental aeration, sunlight restriction, and the proper use of EPA approved aquatic herbicides and algaecides. Physical removal or harvest of weeds and algae is both costly and labor intensive. It is only recommended as a quick fix since cutting, raking, or chopping of aquatic vegetation often causes fragmentation and rapid regrowth. In the case of cattails, it is critical to treat them with an approved herbicide at least 45 days prior to the expected removal.
The physical characteristics of a pond can lessen the effects of typical vegetation management practices. These are generally poorly designed ponds or very old ponds that are filled with sediment. Ponds designed with safety shelves are also prone to severe outbreaks of algae and aquatic weeds. In some cases, complete dredge renovation is the only solution. Note that at all ponds are always moving towards a dry or marsh state. This process called eutrophication is accelerated by population booms and increased land development. As a result, most community storm-water ponds will require periodic dredge renovation.
Pond Owners Should Do Their Part
Below is a list of measures that pond owners and communities can take to help minimize excessive weeds and noxious algae blooms:
- Eliminate or reduce the use of landscape fertilizer near the pond
- Bag all grass clipping and fallen leaves
- Prohibit the feeding of waterfowl
- Maintain a vegetative buffer or “no mow” zone around the pond edge
- Clean up properly after pets
- Tolerate desirable, native aquatic vegetation around the shoreline or littoral zone
- Maintain vegetative cover on the watershed to prevent soil erosion
- Address any erosion concerns early on in their development
- Consider extending the operating times of fountains/aeration systems
Improper Landscaping Practices
Resident Waterfowl Can Impair Water Quality
Soil Erosion Near Pond