Algal Bloom

ocean · freshwater · microscopic life · environment

Algae multiply fast. Algal blooms happen when conditions are just right, like when there's lots of sunlight and nutrients in the water. The algae can double in number in just days, creating thick blankets of color.

Many different colors. Blooms can be bright green, red, brown, or even pink depending on the type of algae. Some blooms are so big and colorful they can be seen from space by satellites.

Sometimes they're harmful. Some algal blooms release toxins that poison fish and can make people sick if they swim in or drink the water. Other blooms are mostly just harmless, like the ones that turn water a pretty shade of red.

Too many nutrients cause problems. Pollution from farms and cities washes extra nitrogen and phosphorus into water, which acts like fertilizer for algae. This makes blooms grow much bigger and more often than they naturally would.

Different types bloom differently. Some algae blooms happen in freshwater lakes and rivers, while others grow in salty ocean water. Marine blooms are sometimes called red tides because they turn the water red or orange.