Why Do Sand Dollars Turn White? The Science Explained

Few things can enchant a shell collector more than spotting a pearly white sand dollar while scouring the shoreline. And if the sand dollar is entirely white, you can rest assured that it’s dead and safe to take home. But how do sand dollars turn white in the first place?

Sand dollars turn white when they wash up on the beach because the sun bleaches them of their color over time. This bleaching occurs once the organic matter falls off a dead sand dollar, exposing the white skeleton underneath, which gets further whitened by the sun.

Sand dollars are exquisitely shaped, and it’s a stroke of good fortune to find a white one on the beach. However, you must ensure they’re completely white before taking them home, and this article will explain why they turn this color. Keep reading to learn more. 

Drying Out

When a sand dollar gets washed up on the beach, it is exposed to the cruel heat of the sun. So if you find a live sand dollar on the beach, it’s best to return it to the ocean immediately to ensure it stays alive. Read my other article to tell if a sand dollar is alive: How To Tell If A Sand Dollar Is Still Alive?

A dead sand dollar will initially appear gray or dull but will eventually turn white as the organic matter falls off and the surface gets bleached. However, an exposed skeleton isn’t the only reason a sand dollar turns white; its ghostly appearance results from constant exposure to the heat and light of the sun.

The Effects of UV Rays

The harsh UV rays of the sun have an aggressive impact on the color pigments on any given surface. These rays are powerful enough to quickly break down the molecular structure of the pigment, causing the color to fade with time.

This degradation of the molecules in pigments is the main reason a sand dollar turns white after prolonged exposure to the sun. And while bleaching is the main reason, a scientific look at this process can tell us more about why sand dollars turn white with time.

Any non-living or dead surface gets its color from molecules called chromospheres that absorb light and reflect it at a particular wavelength. The wavelength at which this light is reflected determines the color we see when we look at the object.

In the case of a sand dollar, its usual color is typically deep red or purple. When a sand dollar gets washed up and isn’t returned to the sea in time, the colors fade as the creature dies. Now, prolonged exposure to the sun damages the chromospheres on the surface of the sand dollar.

As such, the chromospheres gradually lose the ability to reflect any light. Over time, the sand dollar starts to fade and turns completely white as the chromospheres stop reflecting any light.

The fading of pigments through UV rays and the gradual damaging of chromospheres over time are two reasons why dead sand dollars turn entirely white. This and the fact that the only thing left behind is the skeleton of the creature, which is white to begin with.

Fortunately, it’s pretty apparent when a sand dollar is dead as the creature turns completely white. As such, you can safely bring it back home and use it to liven up the decor in your house.

However, you may sometimes find live sand dollars on the beach and be tempted to take them back home. It’s best to refrain from doing so because bringing home live sea creatures is cruel, considering how they suffer without water.

More importantly, taking live marine animals home can affect the ocean’s ecological balance in ways you can’t imagine. These creatures form an integral part of the marine ecosystem, and forcibly removing them from the food chain can have disastrous effects for generations. As such, it’s best to return live sand dollars to their rightful home.

Checking for Signs of Life

There may be instances where you find a dead sand dollar that recently washed up on the beach. In this case, the creature may retain some of its color and appearance, and it can be difficult to tell if it’s safe to take home. Luckily, there are other ways to discern a live sand dollar from a dead one.

Here are a few ways to check for yourself.

Distance from the Water

Sand dollars need water to survive and will die within a few hours of being removed from the ocean. As such, if you find a sand dollar far away from the water, especially during low tide, you can safely assume it’s been dead for a while. Of course, it’s important to look for other signs, but this is the first step to check whether a sand dollar is alive.

Submerged sand dollars have somehow managed to stay in the water and prevent it from being washed up. Sand dollars possess spiny feet that help them dig into the ground and keep themselves from being washed up.

So, in most instances, if you see a sand dollar underwater, it’s safer to assume that it’s still alive and leave it there. However, if you find one on the beach, look for other signs before you decide to take it home.

Lack of Movement

As mentioned in the previous point, sand dollars possess tiny, spine-like feet called cilia. These miniature feet are used to travel across the ocean floor and burrow into the ground. Additionally, a sand dollar uses these feet to move food from the edge of its body to the center, towards its mouth.

Once you’ve picked up a sand dollar, pay attention to its underside and look for movement. If the sand dollar is alive, the cilia will continue to move, and you can see a writhing mass of spines wiggling underneath it.

If you don’t notice any movement instantly, look for areas under the sand dollar where the cilia or feet appear to be clumped together. This clumping occurs when the sand dollar is moving food particles from the edges of its body to the mouth. If you notice movement or clumping, you can bet the creature is still alive and return it to the ocean.

Loss of Color

This sign is the most obvious, and if the sun dollar is bone-white, it is dead and safe to take home. However, there may be instances where a sand dollar appears dull, and you want to look for the other signs mentioned here to confirm whether it’s still alive.

However, if you see a sand dollar that’s purple or reddish, you can rest assured it’s still alive, so return it to the ocean immediately. Conversely, if you find a submerged sand dollar that’s completely white, you can bring it back home, as it is most definitely dead.

Absence of the Yellow Stain

Another obvious way to tell if a sand dollar is alive is by checking your hands to see if the creature leaves a yellowish pigment on it when you pick it up. All you have to do is keep the sand dollar on your palm for up to a minute and observe it.

If the sand dollar is alive, it will secrete a yellowish substance as a defense mechanism. This yellow substance is called echinochrome and is completely safe for humans. In fact, echinochrome has been studied so that it can be used in several medical applications. 

For starters, echinochrome can help soothe the body’s immune response and prevent cytokine syndrome. This condition has been puzzled over by scientists for decades, and this pigment released by the sea urchins is a great lead to a possible solution.

You can read more about sand dollars turning your hands yellow in my other article: Why Do Sand Dollars Turn Your Hands Yellow?

The Bleaching Time

As mentioned previously, a white sand dollar is dead and can be safely taken home. But how long do these creatures take to turn white after they die?

A sand dollar turns white 24 to 48 hours after it is washed up on the beach. This bleaching occurs once the organic matter has fallen off and after prolonged exposure to the sun. If you bring home a sand dollar with some color, you may have to bleach it once more for it to turn completely white.

Final Thoughts

Here’s why a sand dollar turns completely white once it’s washed up on the shore:

  • The harsh UV rays damage the color pigments, wearing them away over time and causing the colors to fade. 
  • Prolonged exposure to sunlight causes the chromospheres to reflect less light, leading to a dulling of the color. Once the chromospheres are too far damaged, they stop reflecting light altogether, creating a white appearance.

Remember that if you find a sand dollar that isn’t white, be kind and return it to the ocean. You’ll be doing a favor to the sand dollar and the environment!

Alexander Picot

Alexander Picot is the principal creator of DiscoveryPit.com, a website dedicated to tips on finding and collecting precious items. Inspired by reading countless adventurer reports from the oldtimers, Alex is passionate about discovering hidden treasures and loves to share his experience with the rest of the world.

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