Miles underwater, the ocean’s clean-up crew finds a feast on the deep seafloor.

The crowned sea cucumber (Peniagone spp.) is abundant on expansive abyssal plains. These squishy sea cucumbers march across the mud on stocky tube feet. They keep their head down, focused on feeding. Thick, flexible tentacles around their mouth probe the sediment in search of food. 

Bits of decomposing animals, poop, and mucus are on the menu for Peniagone. This is not a glamorous diet, but Peniagone provides a crucial ecological service. They are a vital link between the surface and the seafloor, converting organic material sinking from miles above into nutrients for microbes and other seafloor animals.

But this seafloor scavenger is a swimmer too. We sometimes see Peniagone in waters far above the bottom, drifting with slow ocean currents. This behavior might help them reach new and unpredictable food falls more quickly than their bottom-dwelling neighbors.

Peniagone populations go through boom-and-bust cycles on the abyssal seafloor, responding to pulses in organic material raining down from the waters above. MBARI was part of a 30-year study that monitored the abyssal seafloor offshore of Central California. Using a suite of advanced technologies, we saw how bursts of productivity at the ocean’s surface ripple to the communities below.

Our work is revealing humanity’s close connection to the deep sea, and how human actions impact animals and environments miles underwater. 

Mining the deep seafloor for rare minerals creates an uncertain future for Peniagone and thousands of other species that thrive on the sprawling abyssal plain.

All life on Earth depends on a healthy ocean. It helps regulate climate, supports fisheries millions of people depend on for food and livelihoods, and is home to life we are only just beginning to understand. MBARI’s research is providing independent baseline data that policymakers and the public need to weigh decisions about the future of the ocean.