Miles below the ocean’s surface lives an unsung hero in climate change. 

Twisting and turning atop the muddy ooze, the acorn worm (class Enteropneusta) is an unassuming worm-like animal that has a surprising connection to Earth’s climate. Named for their acorn-shaped front end, enteropneusts are actually more closely related to humans than to worms. They have a rudimentary nerve cord similar to ours and breathe oxygen using structures similar to a fish’s gills.

Our team uses advanced robots and time-lapse cameras to study deep-sea acorn worms. Working with collaborators at the Smithsonian National Museum of Natural History and Scripps Institution of Oceanography, we have discovered five new deep-sea enteropneusts and gained valuable insight into the important ecological role of acorn worms on the abyssal seafloor.

A constant rain of particles connects the ocean’s surface to deep-sea communities far below. Carbon dioxide from the atmosphere mixes into the ocean at the surface. Tiny plant-like plankton transform carbon dioxide into organic material, which is then eaten by larger animals. As these animals eat, poop, and die, they create a flurry of organic material known as marine snow. The sinking snow moves nutrients and carbon all the way down to the deep seafloor, where bottom-dwelling animals, like acorn worms, enjoy a bountiful feast. This cycle is known as the biological pump.

Deep-sea enteropneusts roam the seafloor, consuming organic material mixed in the mud. In food-rich areas, they feed in a tight circular pattern. When an area is depleted, they empty their gut to become buoyant so they can float off to a more fruitful patch of food.

In some places, large numbers of acorn worms dot the seafloor. Even when we do not see the worms themselves, we often see their distinctive trails of spiraling poop, revealing their reach across the ocean floor. Scientists think that bottom-dwelling detritivores—animals like acorn worms and sea cucumbers that feed on dead organic material in the mud—are responsible for completely cycling the top layers of sediment within a matter of weeks. 

Acorn worms are connected to us through the carbon cycle. They play a significant role in the redistribution of sediment and nutrients in deep-sea communities. As they do their part to help regulate climate, we can do our part by drastically reducing our carbon dioxide emissions. The ocean is a powerful ally that has buffered us from the impacts of climate change. Now, it is our turn to act on climate change to safeguard the future of the ocean and its inhabitants.