Today’s Wonder of the Day was inspired by Riya. Riya Wonders, “Why are some lakes pink?” Thanks for WONDERing with us, Riya!

On a visit to a foreign country, you hear the locals rave about a nearby lake. A nice dip sounds refreshing, so you throw on your swimsuit, grab a towel, and head for the lake. You arrive and you're ready to dive in, but then you notice something odd.

The lake is pink. We're not talking about a "sunset reflecting off the water"-type of pink. The water looks like a strawberry milkshake. What's going on here?

Pink lakes aren't an optical illusion. They're natural WONDERS that can be found in many countries around the world. Let's take a closer look at what gives these lakes their signature hue.

Some of the most famous pink lakes around the world include the following: Ukraine's Lake Koyashskoe, Tanzania's Lake Natron, Azerbaijan's Masazir Lake, and Senegal's Lake Retba. Australia boasts multiple pink lakes, such as Lake Hillier, Pink Lake, and Hutt Lagoon. Even the northern half of Utah's Great Salt Lake usually exhibits a color that's somewhere between pink and a deep red.

If you were to compare all of these lakes, you would find one interesting factor in common: they're salt lakes. Scientists believe that the high salinity of these lakes helps to explain their unique coloring.

Although the exact cause of each particular lake's coloring hasn't been definitively determined, scientists do have a couple of theories that they believe explain the pink color of these lakes. The key appears to be that the high salinity of these lakes only allows a very few select microbes to grow and thrive in such harsh conditions.

For example, in many pink lakes, the only type of microbe that can survive and thrive is a particular type of halophile micro-algae known as Dunaliella salina. With enough light and heat and a salinity level well above that of sea water, these microbes produce and accumulate carotenoids, such as beta carotene. The color of these carotenoids gives these algae — and the water they populate — their characteristic pink color.

Other scientists have found that pink lakes might also get their color from tiny microbes known as halobacteria. Halobacteria get their rosy pigmentation from a protein, called bacteriorhodopsin, which they use to absorb energy from the Sun (the way plants use green chlorophyll for photosynthesis).

If you ever see a pink lake in person, you may think that your eyes are playing a trick on you. It's not an optical illusion, though. If you fill a plastic bottle with water from the lake, you'll see that the water in your bottle has the same pink color.

Although it might look weird or unsafe, it's perfectly fine to swim in a pink lake. You don't want to drink the water, though. Since the water is so salty, it doesn't taste very good if you accidentally swallow it!

Wonder What's Next?

You might want to bring your calculator to tomorrow’s above-average Wonder of the Day!