Studying creatures that live in total darkness under 4,000 meters of water starts with remote eyes and gentle hands.

Researchers launch ROVs (remotely operated vehicles) — robotic subs fitted with flood-lights, 4K cameras and claw-like manipulators. As the ROV glides a meter above the seabed, it films every sponge, worm and fish in its path. The footage becomes a living census: scientists later freeze-frame the video, count species and map exactly where each one sits.

Next come box corers and push cores — stainless-steel tubes that stab a 50-centimetre plug of mud without stirring it up. Back on deck, lab techs sift the mud through fine sieves to collect tiny clams, brittle-star husks and even single-celled foraminifera. Each organism is preserved in ethanol so taxonomists can examine its shape under a microscope or extract its DNA.

For mobile life like shrimp or jellyfish, teams deploy mid-water nets hung on thousands of meters of cable while acoustic sensors ping schools of animals the camera can’t see.

Water samples are also collected for eDNA analysis: by filtering a few liters, scientists capture stray skin cells and mucus that hold genetic bar-codes, revealing which species passed by without being caught.

Every sample’s depth, temperature and oxygen level is logged so biologists can match species to their preferred micro-habitats.

Repeating the same transects before and after a pilot mining test shows whether animal abundance drops and how fast it recovers.