August 15, 2022 By Katie Roundtree

The term “algae” is generally used to refer to a wide variety of different and dissimilar photosynthetic organisms, generally microscopic. Depending on the species, algae can inhabit fresh or salt water. In modern taxonomic systems, algae are usually assigned to one of six divisions. 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.

Fresh-water algae, also called phytoplankton, vary in shape and color, and are found in a large range of habitats, such as ponds, lakes, reservoirs, and streams. They are a natural and essential part of the ecosystem. In these habitats, the phytoplankton are the base of the aquatic food chain. Small fresh-water crustaceans and other small animals consume the phytoplankton and in turn are consumed by larger animals.

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

Algal blooms are natural occurrences, and may occur with regularity (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 the occurrence of warm, sunny, calm conditions. However, human activity often can trigger or accelerate algal blooms. Natural sources of nutrients such as phosphorus or nitrogen compounds can be supplemented by a variety of human activities. For example, in rural areas, agricultural runoff from fields can wash fertilizers into the water. In urban areas, nutrient sources can stormwater runoff that carries pollutants such as lawn fertilizers.

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 accelerate an algal bloom’s growth significantly. Pollutants from construction runoff, fertilized yards and golf courses, road wash, stormwater runoff, pet waste, and decomposing leaves, grass clippings, and other organic materials also contribute to nutrient imbalances in the water.

Higher temperatures and increased sunlight in summer months also can encourage algae blooms, as does standing water, which is warmer than circulating water and can act like an incubator— another significant influence.

Algae doesn’t necessarily mean poor water quality, but it can be a problem. So, what’s the key to reducing algae on your lake? The most effective thing to do is reduce the number of algae-feeding nutrients, especially phosphorus, that make it into the water. Here are some tips to keep your lake in tip-top shape.

Be careful with fertilizer

Sure, you want a nice green lawn and healthy plants — but that fertilizer you spread in your garden also encourages algae to bloom. It’s best to avoid fertilizer altogether if you’re close to a water source — plant native plants instead, which are well-adapted to the environment and don’t require special maintenance. Implement landscaping strategies, like xeriscaping, that increase groundwater filtration before water enters the pond or lake.

If you must fertilize, try and find a phosphorus-free product, and reduce nutrient rich run-off by applying it when there’s no rain in the forecast.

And don’t think natural fertilizer like manure or compost is any better than a chemical version, anything that’s going to make your garden plants grow is going to make algae grow as well, it’s best to avoid fertilizers generally.

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 are responsible for fueling 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.

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.