Plankton algae occurs naturally as an early stage of the aquatic ecosystem, but it can become excessive and imbalanced in lakes, wetlands, or streams. Most species of this type of algae are microscopic. Some species grow free-floating in the water and some grow on a substrate such as rocks and later release into the water column.
Potentially problematic
Also known as: Green algae, generally known as simply "algae."
Watch for: A blue-green, green, gold, brown, or even red dye in the water. May or may not stick to a paddle. Free-floating, potentially with fowl odors.
Why it happens: Most algae blooms of this sort are attributed to high phosphorus levels in waterbodies. Waterbodies experience excessive algae blooms when there's too many nutrients such as phosphorus free-floating in the water column. Although they're natural, nutrients can become a pollutant in excess. Nutrient pollution comes from stormwater runoff, sediment loading from the surrounding watershed, excessive or improperly applied fertilizer, and/or internal loading (nutrients coming up from the sediment in the lake bed).
How we approach it: Water managers seek watershed-scale efforts to reduce nutrient movements from the landscape. Best Management Practices (BMPs) help to protect soil, slow and halt the movement of stormwater runoff on the landscape, and maintain a balance between upstream and downstream water flows. BMPs include native shoreline buffers, raingardens, stormwater filters, storm ponds, infiltration basins, or introducing high-standing or native vegetation such as prairie plants or alternative lo-mow lawns. In special cases, alum or similar treatments are used to bind the excess nutrients to the lake bottom. Reducing the amount of nutrients that enter storm drains (leaves, grass clippings, etc.) is a great way for the public to help reduce the prominence of algae in our waters.
Private property owners may utilize aeration or fountains to serve as a strategy for pond aesthetics, but these aren't used in the field of water management as they don't address the underlying nutrient causes.
Visit the resources tab for more on Adopt-a-Drain and other practices that help support water quality.
Filamentous algae is a naturally occurring aquatic plant. It grows at the bottom of a pond or wetland and rises to the surface, and it may repeat this cycle multiple times in a season. It tends to stay close to the shore where sunlight can reach the bottom.
Not problematic
Also known as: Macro-algae, pond moss, pond scum
Watch for: Tangles and strings of small filaments of green or greenish-brown or even yellow-grayish material. Can appear as a mat of wet wool or cotton candy. Has more texture than a mat of blue-green algae. Will wrap around or fall off a stick. Usually free floating but can be rooted.
Why it happens: Algae and aquatic plants commonly form in shallow and clear lakes, ponds, and wetlands where sunlight can easily reach the bottom. Filamentous algae has various species that grow in long chains and form visible strings, or filaments. They are actually a large assemblage of various species of phytoplankton, which are microscopic aquatic plants.
How we approach it: Filamentous algae may look unpleasant but are neither good nor bad for wildlife or water quality. Filamentous algae can be manually removed by skimming the surface of the water. Water resource managers prioritize the reduction of phosphorus that enters the water, reducing the amount of fuel for algae of all types to grow. The public can support these nutrient reductions by limiting excess nutrients that enter the water. This can be done by reducing the pollution that travels through storm drains, avoiding spraying grass clippings onto the street, and maintaining a buffer of high standing vegetation on shorelines.
Copper sulfide treatment is sometimes used to limit this type of algae, but VLAWMO does not recommend this practice as the substance is classified as toxic under the Minnesota Department of Health.
Blue-green algae is a certain type of cyanobacteria that can produce a toxin called microcystin. It is harmful to people and pets. There is no way to visually identify whether a particular blue-green algae bloom contains toxins. Water and health professionals give the following advice to the public: "When in doubt, keep out!"
Problematic
Also known as: Blue-green algae, cyanobacteria
Watch for: Thick pea soup or green paint, floating mats of scum. Fowl odors more pungent than plankton/green algae. Tends to stick to a paddle or can be lifted by a paddle.
Why it happens: A blue-green algae bloom can occur anytime during the summer into September, and is usually associated with warm weather and low rainfall. An abundance of plankton algae raises the risk of a blue-green algae bloom.
How we approach it: Water resource managers generally utilize the same procedures for blue-green algae as they do for plankton/green algae. There is no immediate treatment for cyanobacteria, as water and health professionals use a method of awareness and selective testing when needed. The public can support the risk of blue-green algae blooms reducing nutrient runoff in the form of fertilizers, organic debris such as leaves, grass clippings, and other yard waste. Avoid contact and don't allow pets to swim in or drink water with a suspected blue-green algae bloom. Blue-green algae blooms in the watershed are reported to the Minnesota Department of Health.
Visit the resources tab for more on Adopt-a-Drain and other practices that help support water quality.
Aquatic plants are an important part of the aquatic ecosystem, providing food and habitat for insects, fish, and birds. They also play a key role in the balance of nutrients such as phosphorus. Aquatic plants hold and contain nutrients in the plant as well as the roots, and play a key role in maintaining good water quality.
Not problematic
Also known as: Macrophytes
Watch for: Stems, branches, or leaves. May or may not break the water's surface. Usually rooted but can be free floating.
Why they happen: Aquatic plants tend to grow where sunlight can reach the bottom of the lake, pond, or wetland. An aquatic seed bank is similar to a forest or prairie, with a diverse array of native plants that can potentially fill a habitat. Aquatic plants can include tiny, floating plants that blanket the water surface such as duckweed, watermeal, and spatterdock.
How we approach it: Water resource managers promote a clean water state for lakes, ponds, and wetlands. Organizations such as VLAWMO are charged by law with the task to conduct efforts that support good water quality. For shallow lakes, water quality is either in a clean, plant-dominated state or a turbid (murky), algae-dominated state. It is very difficult for a lake to move from a turbid state to a clean state, but very easy to move from clean to turbid.
Aquatic plants can be dense to the point of hindering boat movement and fishing in shallow lakes and wetlands. We understand that these situations can be frustrating but ask communities to consider the following options for aquatic plant management:
- The Minnesota Department of Natural Resources allows manual aquatic vegetation harvesting under 2,500 sq ft or spanning less than 50 feet of shoreline. A permit is required if harvesting exceeds these measurements.
- Chemical treatment by permit may be possible or recommended for specific Aquatic Invasive Species (AIS).
- Adjust expectations for shallow freshwater, adapt recreation to the type of habitat, or wait until plant growth declines with the change of weather.
