Why are some lakes full of algae and thick plants?

Plants naturally grow in and around lakes, but sometimes lakes and ponds can get an overgrowth of plants, algae, or bacteria. In many cases, humans are responsible. Chemicals that are used on lawns and in agriculture (like nitrogen and potassium) wash into our water systems. Once there, plants and algae have a feast on this “food”.

Sometimes overgrowths of cyanobacteria (called “blooms”) can make the water scummy and turn it a blue-green color (or other colors). Cyanobacteria produce compounds that impact the taste and odor of water, make fish unpalatable, and even produce toxins that affect human health. Scientists are still studying the causes of these blooms.

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Image: Algae Sampling in Rapid Creek near Rapid City, SD
May 9, 2007

Algae Sampling in Rapid Creek near Rapid City, SD

U.S. Geological Survey hydrologists preparing periphyton algae samples from rocks collected in Rapid Creek.

View of cyanobacterial bloom on Milford Lake, Milford, KS, July 2016
November 30, 2000

Cyanobacterial bloom on Milford Lake, Milford, KS, July 2016

View of a cyanobacterial bloom in Milford, Kansas.

Image: Harmful Algal Blooms

Harmful Algal Blooms

You may notice a green, red or brown film on your favorite boating or swimming area in the summer. This coloring could mean that the water is affected by harmful algal blooms. Harmful algal blooms are an accumulation of tiny organisms known as algae and can release harmful toxins into the environment. Pictured here is Binder Lake in Iowa covered in algal blooms.

Image: Harmful Algal Blooms

Harmful Algal Blooms

You may notice a green, red or brown film on your favorite boating or swimming area in the summer. This coloring could mean that the water is affected by harmful algal blooms. Harmful algal blooms are an accumulation of tiny organisms known as algae and can release harmful toxins into the environment. Pictured here is a bloom on the shore of Lake Dora, FL.

Image: Harmful Algal Blooms

Harmful Algal Blooms

You may notice a green, red or brown film on your favorite boating or swimming area in the summer. This coloring could mean that the water is affected by harmful algal blooms. Harmful algal blooms are an accumulation of tiny organisms known as algae and can release harmful toxins into the environment. If you see a bloom, avoid the area. Pictured here is a beach on Marion

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Image: Harmful Algal Blooms

Harmful Algal Blooms

You may notice a green, red or brown film on your favorite boating or swimming area in the summer. This coloring could mean that the water is affected by harmful algal blooms. Harmful algal blooms are an accumulation of tiny organisms known as algae and can release harmful toxins into the environment. Pictured here is Binder Lake in Iowa covered in algal blooms. One of the

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Algal Blooms in Lake Okeechobee

Algal Blooms in Lake Okeechobee

Landsat images captured in 2016 show algal blooms in Lake Okeechobee pop up during the summer. These blooms can adversely affect drinking water, recreation, tourism, and local wildlife. Credit: Landsat 8