Algal bloom in Lake Erie

Harmful Algal Blooms: What Are They, and What Can You Do About Them?

A tide of red washes over a lake, dyeing the water a crimson color. While some people may be more familiar with the crimson tide you see at an Alabama football game, this scenario, dubbed the “red tide,” can occur far outside of the Yellowhammer State. 

The idea of blood-red water might seem surreal, but this environmental phenomenon occurs in many places across the United States, from Florida to Maine. This happens when algae—organisms that live in bodies of water and are generally microscopic—grow rapidly and dominate the water surface. Usually algae plays a vital role in ocean and freshwater habitats, providing food to countless aquatic critters. Blooms—or explosions of algae growth—are often harmless, but large outbreaks of algae can occasionally be catastrophic.

As an algae colony grows, dies, and begins to decompose, it uses up lots of oxygen. This depletes the oxygen supply and leaves little left for fish and other marine life, causing many of these animals to die. Some algae, such as the ones that cause the “red tide,” release toxins that are absorbed by shellfish and other creatures. These toxins build up in the ecosystem, harming wildlife that come into contact with the contaminated water. When these algal blooms grow out of control, they can also become a public health hazard.

Harmful algal blooms can cause human illness, decimate fisheries, and devastate lakes, beaches, and other recreational areas. The biggest cause of harmful algal blooms is nutrient pollution, or the excess of minerals like nitrogen and phosphorous in the environment. Increased levels of nutrients in the water can feed larger algae colonies, leading to these large-scale blooms. Nutrient pollution can be exacerbated by human activities, ranging from agricultural runoff to pollution from household cleaning products.

Here is what you can do to protect your water resources:

  • Use water efficiently, such as by taking shorter showers and turning off faucets when not in use.
  • Limit fertilizer use, which causes the buildup of nitrogen and phosphorous in waterways.
  • Use phosphate-free cleaners, detergents, and soaps to avoid fueling harmful algal blooms.
    • Check out this Safer Choice search engine from EPA to make environmentally friendly shopping easier!

Learn more about what people in your community are doing to cut down on nutrient pollution here.