algal bloom

Monitoring Harmful Algal Blooms? There’s an App for That!

By Annie Zwerneman

Algal bloom covers a lake.

Algal bloom covers a lake.

I was recently on my favorite hiking trail, which passes by a beautiful lake. But this time hiking past it, I noticed a strange, dark scum creeping along the shoreline of the water. I learned later that this scum was actually an algal bloom: a population of algae increasing quickly over a short period of time.

Some algal blooms are merely an eyesore, but others fall into a more serious category called “harmful algal blooms” (HABs): algae and cyanobacteria (formerly known as blue-green algae) that remove oxygen from the water, crowding their way along the surface and producing toxins that are harmful to animals. The toxins that HABs produce can affect peoples’ health, too.

EPA has been working to monitor HABs, including taking water samples to see where and how algal blooms may affect you. Unfortunately, taking such water samples is time-intensive, so EPA has been working alongside scientists at the National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and the United States Geological Survey (USGS) to find new ways to monitor the quality of inland water bodies, such as lakes and reservoirs. EPA hopes to monitor estuaries and coastal waters in the future as well.

A new Android app is being developed that displays imagery of cyanobacterial cell counts in freshwater systems, which can indicate the presence of HABs. Expected to be in beta testing this fall, the app will provide information necessary for locating and monitoring HABs. It’s primarily aimed toward stakeholders like health departments and municipalities (such as water treatment plants).

The app will display data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. In the near future, EPA researchers hope to incorporate the European Space Agency’s Sentinel-3 and potentially the Landsat-8 satellite as well. They will work with their NOAA, USGS, and NASA partners to pull all these capabilities together once the app is ready for public use.

The way the app will work is a bit like the weather station. At the beginning of each week, the cell count will be updated based on the satellite information gathered the previous week. There may even be a prediction of the cell count for the upcoming week available. For example, you can get a cell count in Lake Erie for the current week, and then get a prediction of what the cell count may be next week.

Thanks to the collaborative effort of multiple federal agencies, those looking for information about freshwater quality and HABs won’t have to look far: there will be an app for that!

About the Author: Annie Zwerneman is a 2014 summer intern working for the EPA’s Office of Research and Development.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Keeping Pets—and People—Safe from Toxic Algae

Visible green slime in Lake Needwood during harmful algal bloom outbreak in September 2012.

By Patty Scott

Two years ago, our family planned to take our Yellow Labrador puppy Fiona to Lake Needwood near our home in Rockville, Maryland for a swim. Our puppy needed somewhere to exercise and the scenic lake near Rock Creek Park seemed like the perfect place. My husband, however, mentioned something about a warning for a harmful algal bloom. At the time, I had just started working on EPA’s National Lakes Assessment, the agency’s report card on the condition of the nation’s lakes, and thankfully knew about the dangers of harmful algal blooms. Blue-green algae can produce harmful toxins that can be fatal if ingested. Since people are not allowed to swim in Lake Needwood, the dangers are not as great for humans. However, dogs are especially at risk if they swim in or drink the water. We decided against taking Fiona anywhere near the lake.

While Montgomery County did not know the cause of the outbreaks in Lake Needwood, harmful algal blooms are often triggered by excessive levels of the nutrients nitrogen and phosphorus. Many of our lakes, rivers, streams and bays are becoming overloaded with nutrients from a wide range of sources. Excess nutrients spur the growth of algae to the point where they can explode into vast — and sometimes toxic — colonies of slime. Algal blooms often peak during the summer months, but in some parts of the country they occur year round.

Nutrient pollution is a growing concern because it threatens public health, recreation and our economy. National data is not easy to find on impacts to our four-legged friends, but sadly dog deaths have been reported due to harmful algae.

Warning sign advising residents and their pets to avoid direct contact with the water at Lake Needwood in Montgomery County, Maryland.

Like many pet owners, we treat Fiona and Jake, our other lab, like part of our family, and we’d be devastated to lose them. It’s best to keep pets away from the water anytime there is visible surface scum, if the water is discolored or if there is a strong musty smell. Also, keep in mind that not all waters are monitored. You can check EPA’s new How’s My Waterway app to find out about the condition of your local waterway and whether it’s been tested.

Everyone can help make a difference. One easy way to combat algae is to take care not to over-fertilize. And always remember to pick up pet waste. To learn more about how you can prevent nutrient pollution, visit

About the author: Patty Scott works in EPA’s Office of Wetlands, Oceans and Watersheds on communications and outreach.  She loves fishing, kayaking, cycling and other outdoor pursuits.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.