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How Do Sea Cucumbers Poop?

Coral reefs are built on sea cucumber poop

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© Kristin Hettermann

The ocean has a few do-gooding superstars. Take the oyster for instance. An oyster can filter up to 50 gallons of water per day making the reefs they live in cleaner for all. Seagrass can alleviate ocean acidification while creating habitat and vital oxygen for the sea creatures that live among it. Well, I’d like to elevate one humble creature up to these esteemed ranks: the sea cucumber.

If you are an avid reader of this blog (and why wouldn’t you be!?), you know I have a special place in my heart for sea cucumbers. I’ve always been fascinated by the fact that they can shoot out their organs at predators and regrow new ones. Well, now I am in awe of another thing they expel: their poop.

Please buckle up kids, let me put on my Miss Frizzle wig and take you on a ride into the digestive system of an animal that looks like a pickle you need to throw out but is, in fact, a reef savin’ superhero.

Let’s take a trip to the sea cucumber’s anus where it both defecates and, in a horrific curse of evolution, also breathes. In the course of a year, a sea cucumber butt will expel 30.8 pounds of poop. As a comparison, sea cucumbers only weigh 0.1 to 5 pounds so they poop more than six times their weight every year.

Sidebar about the sea cucumber’s butt: it actually can be a home for the peculiar star pearlfish. That’s right—this multifunctional hole also serves as a lovely seaside escape for an eel-like fish. Are you squirming? Because I am. The pearlfish finds a sea cucumber by following their smell and the gentle currents created by the sea cucumber’s unique breathing technique. As the sea cucumber exhales, the fish dives headfirst into its anus using what one scientist called “violent strokes of the tail.” Some species of pearlfish just hang out there but there is one species in particular that then begins to eat the host from within. Imagine that horror movie: “the call is coming from inside the” … well, you know.

Okay, so why is this sea cucumber poop important? For that answer, we need to look to the front end of the sea cucumber. The sea cucumber has a ring of tentacles (technically they are modified tube feet) around its mouth that help it gather food. Sea cucumbers feed on algae and other tiny particles they find in sediment on the ocean floor.

Any gardener knows that worms are good for gardens. Earthworms help to recycle nutrients by feeding on organic matter (like leaves, fungi or dead plants) and break it down into nutrients that fertilize the soil. Sea cucumbers function similarly. They break down the particles they eat and help recycle nutrients back into the ocean ecosystem like nitrogen, ammonia and calcium carbonate. Just like earthworms, they also can help aerate the sediment as they are hunting for food, which releases even more nutrients and can create safe habitats for other animals like crustaceans.

Remember how I said sea cucumber poop includes calcium carbonate? Well, that nutrient helps coral skeletons grow as it is essential to coral reef formation. Sea cucumber poop is basic which means it is best formed when they drink pumpkin spice lattes. Just kidding! The poop is considered basic in terms of pH which means they can ever so slightly lower the acidity of surrounding waters which also helps coral grow their skeletons. Researchers found that sea cucumbers can produce more than 64,000 metric tons of poop in a single coral reef over the course of a year. That’s the weight of five Eiffel towers—though not exactly something any tourist would want to see. All that poop is vital for the health of the reefs they live on.

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©  NOAA OKEANOS EXPLORER

Every superhero has a villain and unfortunately for the sea cucumber, their survival is threatened by overfishing and illegal trade. Sea cucumbers are considered a delicacy or even an aphrodisiac in some areas which has fueled illegal capture and smuggling of these important little creatures. Some sea cucumbers are now endangered species, threatening not only their populations but all the marine life that rely on their important role in reef ecosystems.

Everyone poops. But the sea cucumber gets to contribute to ocean health in the process. They are a great reminder that even a small, strange living tube of a thing is vital to ocean health.

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