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Why are some lakes I see full of algae and thick plants?

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Welcome to CoreFacts, where we're always short on time and big on science. I'm Steve Sobieszczyk. Let's get right to it, today's question is

Why are some lakes I see full of algae and thick plants?

In many cases, humans are responsible. Actually, these lakes are being fed too much food for plants! There are certain chemicals we use that are nutrients (or food) to plants. At our homes we fertilize our yards with nitrogen, potassium, and phosphorus. These chemicals wash off our lawns and eventually get into the water system, such as into creeks, rivers, and lakes. Once there, algae and plants have a feast on this "food". Things used to be worse for our water bodies. Phosphorus used to be an ingredient in our laundry detergent, but this has generally been phased out.

And now you know. Join us again tomorrow as we'll give you yet another new CoreFact. If you're interested in previous CoreFacts, or would like to check out CoreCast, our in-depth science podcast, browse over to If you would like to contact us here at the show or submit a question you think we should answer on the air, you can email us at or leave us a voicemail at 703-648-5600. Remember, long distance fees do apply.

The USGS CoreFacts is a product of the U.S. Geological Survey, Department of the Interior.

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