Picture of ARMS in Papua New Guinea

Two ARMS sit on the ocean floor.
(Laetitia Plaisance, Smithsonian)

In order to study the reefs in Papua New Guinea, scientists use devices known as Autonomous Reef Monitoring Structures (ARMS). The ARMS have eight layers of plastic plates that mimic the structure of coral reefs, attracting species of sponges and algae, as well as crabs, mollusks and other small invertebrates. Researchers install the ARMS onto the reefs at different distances away from the CO2 seeps and leave them there for one to two years.