Rainbow River

What’s going on with this multicolored river?
Pick the explanation you think is correct. Give three reasons to support your answer.

A. People dyed the river to celebrate a holiday.

B. The river has become polluted by toxic chemicals.

C. Colorful plants that grow in the river make rainbow shades.

Pause your scrolling. Think about three reasons to support your answer.

Now let’s find out what’s really going on . . .

If you answered C, you’re right!

Rainbow River. Liquid Rainbow. River of Five Colors. It’s easy to see why the Caño Cristales, a river in Colombia, has earned these nicknames. The vibrant hues seen here are the result of an aquatic plant called Rhyncholacis clavigera. It grows only on rocky riverbeds in this area of Colombia. It changes colors throughout the year.

For most of the year, the river is an ordinary-looking combination of greens, grays, and browns. The chlorophyll in R. clavigera usually gives it a green color. This substance absorbs sunlight, which the plants use to make energy. This process, called photosynthesis, uses carbon dioxide gas and water to produce sugar the plants use as food.

When conditions in the river change, R. clavigera does too. This usually happens from September to November—between the wet summer and dry winter seasons. Falling water levels and increased sun exposure trigger the plants to turn colors. Depending on the conditions in different parts of the river, the plant may be pale green, light rose, or a whole range of vibrant reds, yellows, and purples!