Written by Michele Weber

Tube sponges in water

Colorful red finger sponge and brown tube sponges on Belize reef

If it weren’t for the diet of the humble marine sponge, reefs might be rather boring places.

Image: Thinkstock

Coral reefs have much in common with rainforests: both are full of life, but are low in nutrients. How is that possible? As far as a coral reef goes, it’s because marine sponges produce waste that contains food that other reef animals can eat.

Ecosystems such as the Great Barrier Reef are home to many different animals: corals, worms, crabs, octopus, fish, sharks, and … sponges. It is hard to imagine a marine sponge as an animal, but they are made of many cells that work together to catch other living things for energy. They are also really important for coral reefs.

A new discovery shows that sponges suck up tiny bits of food floating around in the ocean that bigger animals can’t eat, and spit out waste that small animals such as worms feed on. The worms get eaten by octopus or fish, which then get eaten by bigger fish, and so on. Known as a food chain or food web, sponges help kick-start the chain that keeps the reef alive.

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