June 17, 2024 By Katie Roundtree

Algae generally refers to a wide variety of different and dissimilar photosynthetic organisms, typically microscopic. Algae can inhabit fresh or salt water and are classified into one of six divisions, usually known by color, such as green, red, brown and golden. The misnamed blue-green algae are often grouped with algae because of the chloroplasts contained within the cells. However, these organisms are actually photosynthetic bacteria assigned to the group cyanobacteria.

Freshwater algae, also called phytoplankton, vary in shape and color and are found in many habitats, such as ponds, lakes, marshes and canals. They are a natural and essential part of the ecosystem. In these habitats, phytoplankton are the base of the aquatic food chain. Small freshwater crustaceans and other small animals consume phytoplankton, which in turn is consumed by larger animals.

Under certain conditions, several species of true algae as well as cyanobacteria, are capable of causing various nuisance effects in fresh water, such as excessive accumulations of foams, scums, and discoloration of the water. When algae in a lake or a canal increases explosively, an algal “bloom” results. Lakes, ponds, marshes and slow-moving canals are most susceptible to blooms.

Algal blooms are natural occurrences and may occur regularly (e.g., every summer), depending on weather and water conditions. The likelihood of a bloom depends on local conditions and characteristics of the particular body of water. Blooms generally occur where there are high levels of nutrients present, together with warm, sunny, calm conditions. However, human activity often can trigger or accelerate algal blooms. Various human activities can supplement natural sources of nutrients such as phosphorus or nitrogen compounds. For example, agricultural runoff from fields in rural areas can wash fertilizers into the water. In urban areas, nutrient sources in stormwater runoff carry pollutants such as lawn fertilizers and grass clippings.

Algae growth depends on weather patterns, temperature, and nutrients in the water. While blooms happen naturally, an imbalance of phosphorus and nitrogen, in particular, can significantly accelerate their growth. Pollutants from fertilized yards and golf courses, road wash, stormwater runoff, pet waste, decomposing leaves, grass clippings, and other organic materials also contribute to nutrient imbalances in the water.

Higher temperatures and increased sunlight in summer months can also encourage algae blooms, as can standing water, which is warmer than circulating water and can act like an incubator.  Algae in a lake does not always indicate poor water quality, but it can cause problems. The best way to reduce algae growth is by minimizing the amount of nutrients, such as phosphorus, that can feed it and enter the water. Here are some tips to help maintain a healthy lake:

Be careful with fertilizer

If you want a lush green lawn and healthy plants, you may be tempted to use fertilizer in your yard or garden. However, the use of fertilizer can have negative effects on the environment, especially if you are close to a water source. Fertilizers may encourage the growth of algae when they enter the water bodies, which can harm aquatic ecosystems.

It’s best to avoid using fertilizers altogether and instead choose to plant native plants that are well-suited to the local environment. These plants will not require special maintenance and will also contribute to the health of the local ecosystem. Additionally, implementing landscaping strategies like xeriscaping can help to increase groundwater filtration before water enters nearby ponds or lakes.

If you must use fertilizer, try to find a phosphorus-free product and apply it when rain is not forecast. This can help to reduce nutrient-rich runoff. However, it’s important to note that even natural fertilizers like manure or compost can contribute to the growth of algae, so it’s best to avoid using fertilizers whenever possible.

Properly dispose of organic materials

Following yard work, leaves, grass and other debris should be bagged and removed from the property to prevent them from accumulating and decaying in the waterbody. When organic materials are allowed to decompose in freshwater resources, they release undesirable nutrients that fuel nuisance plant and algae growth. Ask your lawn-care company to remove grass clippings and leaves to prevent decomposition in or around ponds and lakes. Do not mow, rake or blow grass clippings into the nearby waterbodies.

Pick up and dispose of pet waste, a common source of excess nutrients and bacteria. Don’t throw pet waste bags into lakes and canals. They will eventually break down and release those toxins into the waterway.