9 Surprising Facts About the Humble Oyster

oyster bed popping out of water at base of boardwalk support

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Oysters may be small, innocuous creatures, but there is a lot to them. They have been mixed into soups and stews as peasant food, as well as considered fit for a king (Louis XIV of France was a fan of slurping them raw). In the modern day, they are valued not only for their taste but also for the impactful ways they serve the environment.

There's more to know. Here are nine facts that will show you how interesting these coastal mollusks can be.

1. They Can Hear

In research conducted in 2017, scientists subjected oysters to both high- and low-frequency sounds. The oysters did not respond to the high-frequency sounds. However, the low-frequency sounds — such as those made by ships, human-caused explosions, and wind turbines — caused the oysters to clamp their shells closed to keep out the noise pollution.

Shutting out noise may provide oysters with peace and quiet, but it also limits their ability to know what's going on around them, from rainfall to water currents. This can have serious negative impacts because oysters depend on those cues to start certain important biological processes, such as digestion and spawning.

2. Oyster Eating Is Ancient

Modern humans are not the first to consume oysters as food — not by a long shot. In fact, when archaeologists locate a pile of oyster shells, they know they aren't far from a human settlement. Oyster shell heaps (called middens) have been dated back to 3600 BCE, and oyster eating has thousands of years of history among Native Americans along both coasts. It's also part of the historical record in ancient Egypt, Greece, and Rome; medieval France and England; and Mayan culture.

3. The Shells Are Good for Your Garden

close up of heaping pile of discarded empty oyster shells

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When crushed, oyster shells can play a valuable role in horticulture as a soil additive. They contain high quantities of calcium, which helps to balance pH levels in soil, improve fertilizer intake, and strengthen plant cell walls.

Because of their coarse texture, crushed oyster shells also encourage water flow throughout soil by preventing the soil from compacting. Another benefit of this texture is that it turns away garden pests like moles and voles that could damage plants.

If you wish to use crushed oyster shells for your garden, they are available for purchase. For maximum sustainability, you can try collecting some yourself (if you live on a coast) or even reach out to a local seafood restaurant that may be willing to offer you its daily shell waste.

4. They Are Mentioned in Shakespeare Plays

"The world is your oyster" is a common motivational phrase to encourage someone to see all the opportunities that lie in front of them. It's exciting to see oysters be featured in everyday conversation, but that spotlight was originally shone on the creature by one of the most famous writers in history, William Shakespeare.

In "The Merry Wives of Windsor," one character says, "Why then, the world's mine oyster, which I with sword will open." While we've done away with the violence of using a sword to open the figurative oyster of possibilities, the sentiment has stayed with us.

Lesser known is the oyster reference in "As You Like It," when the clown Touchstone says, "Rich honesty dwells like a miser, sir, in a poor house, as your pearl in your foul oyster."

5. They Clean the Water

Every day, a single oyster filters approximately 50 gallons of water. When oysters pull water over their gills, the gills trap nutrients and algae. As a result, the water exits the oyster cleaner than how it entered.

Because of these filtration abilities, oysters have been looked at as potential solutions to water pollution. In 2017, New York State invested $10 million in the expansion of oyster seeding in an attempt to improve water quality along the coast of Long Island.

6. Groups of Oysters Create Habitats for Other Sea Life

clumps of oysters on rocks and sea floor at low tide

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Once oysters pass the larval stage, they attach themselves to a solid surface where they will remain for the rest of their lives. These surfaces can be piers, rocks, or even other oysters to form reefs or beds.

When oysters multiply across an area, their reefs provide anchors for other sea life to attach to, such as sea anemones and barnacles. In turn, those attract small fish and shrimp, which then invite larger fish.

7. They Protect Against Climate Change

We know that oysters filter water, but just as important as the resulting clean water are the things that they filter out of it — namely nitrogen, which typically enters water as fertilizer runoff. Although discussions around climate change typically focus heavily on carbon, the impact of nitrogen should not be ignored — nitrous oxide is over 300 times more potent than carbon dioxide, and it is ranked third on the list of threatening greenhouse gases.

Research has suggested that a healthy oyster habitat can reduce added nitrogen in water by up to 20 percent, making oysters a strong line of defense in the fight against climate change.

8. They Can Keep You From Catching a Cold

close up of woman eating an oyster out of its shell with spoon

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Zinc is a mineral essential to immune function — it can protect you from the common cold and even the flu. And oysters are packed full of it. In fact, they have the highest amount of zinc of any food source; with 5.5 milligrams, a single oyster contains more than half the recommended daily allowance of zinc for adults. So come cold and flu season, they could be a helpful treat.

9. Many Oyster Populations Are Declining

In many places, oyster populations are declining dramatically. One study found that in Maryland, the number of adult oysters has declined by about 50 percent between 1999 and 2018. In some places, the oyster population has decreased so much that they have been labeled locally extinct. This is due to a combination of overharvesting and disease.

The hope is that because of the important services they provide — from water filtration to fighting climate change to supporting local economies — conservation efforts will ramp up.