Algal blooms

Algae are tiny plants that live in water. Sometimes when there's a lot of nutrients in the water, like fertilizer from lawns or farms, the algae can grow really fast and make a lot of plants called an algal bloom.

It's kind of like when you put too much food in a fish tank and the fish poop a lot, making the water dirty. Algae like dirty water and they grow really fast in it.

But too much algae can be bad for other plants and animals that live in the water. When there's so much algae that it covers the surface of the water, it can block out the sunlight that other plants and animals need to live.

Sometimes, the algae can also use up all the oxygen in the water, which can be really bad for fish and other creatures that need oxygen to breathe.

So even though algae are good in small amounts, too much of it can be bad for the environment. That's why people try to keep the water clean and not use too much fertilizer or other things that can make the algae grow too much.