It’s Complicated. The Amazing Relationships of the Deep

Life is tough when you live thousands of meters below the surface of the ocean clinging to the sides of ancient underwater volcanoes. You might even say the pressure is crushing, so who are we to judge the complicated relationships that form in these extreme conditions. Sometimes you just need a little help from your friends.

Shark swims along seafloor as small sub follows
ROV pilots “fly” down to depths of up to 3,000 meters to film some incredible creatures of the deep, like this shark. Photo by OET / Nautilus Live

The translucent Deepstaria jelly is a rarely seen deep sea creature. The Deepstaria lacks stinging tentacles and so it traps prey inside its large bag-shaped bell. This method works well for Deepstaria, but it also creates a perfect opportunity for stowaways. If you look closely in this Deepstaria you can see a small red isopod. Similar to a pillbug — isopods can often be found living inside the Deepsatria’s bell cavity!

pink jellyfish against big rock
A bright red isopod lives within the bell — or body — of the Deepstaria jelly. Photo by OET / Nautilus Live

This full extent of this relationship isn’t understood, but the isopod seems be be getting a safe ride as well as a meal out of the arrangement. It likely eats small bits of the jellyfish or food trapped in the large body of the jelly! Look, it’s not a perfect relationship, but who are we to judge?

Thousands of meters below the waves of the central Pacific Ocean sponges in the genus euplectellidae have silica in their tissues that give them a delicate but rigid architectural appearance. In fact, the sponges form an excellent home for certain species of crustacean. The prospective sponge residents move in when they are small enough to fit between the complicated internal structures of the sponge, then stay there until they become too big to leave and are trapped.

White object whose innards look like webbing
A glass sponge in the family euplectellidae. Photo by OET / Nautilus Live

Often pairs of the shrimp will live together, confined inside a glass sponge castle their entire lives. But it’s not all that bad. The sponge provides the shrimp with a safe and stable home, while the shrimp “clean” the inside of the sponge by feeding on the waste of the sponge. To each their own, we guess?

Ancient deep sea corals are creating whole neighborhoods among their branching arms. The corals which can be hundreds or even thousands of years old are composed of many individual polyps and each polyp is a separate animal! Like many deep sea creatures, these corals filter their food from the swirling currents that form underwater rivers across the surface of the deep.

purple flowery object with orange worms in itand white object below
Victorgorgia (bright purple coral) with at least one brittle star perched in its branches and a primnoid coral behind it. Photo by OET / Nautilus Live

Crinoids, also called sea feathers or sea lilies, will climb the coral branches like deep sea trees, likely in order to get higher up into the current where they feed. Squat lobsters, hermit crabs and brittle stars all use the coral the same way, anchoring or perching in the branches of the coral assemblages. Some of these species seem to benefit from the arrangement, but others may just be using the coral as a convenient perch.

orange spider-looking things crawl over white coral
Crinoids and squat lobsters perch in the branches of a large black coral in Howland Island National Wildlife Refuge. Photo by OET / Nautilus Live

The relationships between the members of these deep sea assemblages are still being explored! What we do know is that in the seemingly desolate expanse of the deep sea, communities of life are forming and thriving thanks to some complicated relationships.

Our public lands and national wildlife refuges protect an amazing array of wildlife — and when you can’t visit the bottom of the ocean floor, a virtual visit is the next best option! The images being beamed up from the seafloor were being watched simultaneously by scientists, enthusiasts, and ocean fans across the world on Life may have started in the ocean, but given the distances and difficulty of studying the ocean floor there is still a lot to discover.

The E/V Nautilus uses muti-beam mapping and remote operated vehicles to explore the ocean floor. The research and information collected on this trip will improve scientists’ understanding of marine habitats, seafloor composition, and the geologic history of these areas. The Ocean Exploration Trust, which operates the E/V Nautilus, was awarded a grant from the NOAA Office of Ocean of Exploration and Research for the E/V Nautilus to conduct the 2019 Pacific expedition.

These images are from the Pacific Remote Islands Marine National Monument, which protects entire thriving ecosystems — from deep sea volcanic features to island seabird colonies — and includes seven National Wildlife Refuges: Baker, Howland, and Jarvis Island; Johnston, Wake, and Palmyra Atoll; and Kingman Reef.

By Holly Richards, an External Affairs officer in the U.S. Fish and Wildlife Service’s Pacific Islands Fish and Wildlife Office and a passenger on the E/V Nautilus.

We’re dedicated to the conservation, protection and enhancement of fish, wildlife and plants, and their habitats.