Sponge waste keeps coral reefs alive!

By Casey Frye, CCNN Writer

sponge waste
This is a picture of the sponge Halisarca Caerulea. You see all the sandy white streaks caking the outside? Yeah, that’s poop!

When I think of coral reefs, images of bright fish, warm oceans, and colorful underwater environments swim through my mind. Believe it or not, corals are actually living organisms in one of the world’s most complicated ecosystems.

Eco-what? An ecosystem is the relationship shared by living creatures and their environment. In this case, the entire ecosystem is referred to as a coral reef.

As you can imagine, it takes a lot of food to feed all of the beautiful animals. Heck, just think about how much you eat in a single day! However, while you might have the luxury of a fridge filled with tasty snacks, where exactly do coral reefs get their nutrition from?

The mystery behind these strange underwater kingdoms is called Darwin’s Paradox, and gets its name from Charles Darwin (the father of evolution science) and the word paradox (two opposite ideas being true at the same time). For over 171 years, scientists hadn’t solved this unique puzzle… until now. The answer’s pretty hilarious, too, because it looks like sponge poop is responsible for keeping coral reefs alive!

Wait, how is it that the thing I use to clean my dishes is responsible for keeping entire communities thriving? Well, it’s not that kind of sponge! In this case, I’m talking about the ones that live in coral reefs.

Okay, so how do these squishy sea creatures create life with their yucky poop? First, they eat waste from algae and corals, digest what they need from the meal, and release the rest out of their bodies. This may sound gross to us, but for the different animals living underwater, it’s a delicious treat to fill their hungry bellies. The researchers refer to this entire process as a “sponge loop.”

Since the answer’s so simple, it seems kind of silly that it took brilliant researchers 171 years to figure out the answer. Well, lead author Jasper de Goeij, an aquatic ecologist at the University of Amsterdam, explains, “Up until now no-one has really paid sponges much attention. They look nice, but everybody was more interested in corals and fish… but it turns out that sponges are big players – and they deserve credit for their role.”

Featured image courtesy of USFWS Pacific on Flickr. Image of sponge courtesy of Royal Netherlands Institute for Sea Research.