This “frame grab” from video taken by MBARI’s remotely operated vehicle (ROV) ‘Doc Ricketts’ shows the robotic arm from the ROV lifting a sea urchin out of the experimental chamber of the deep FOCE system. Within this chamber, deep-sea urchins were exposed to seawater with slightly lower pH (more acidic) than the surrounding seawater for weeks at a time, while researchers on shore monitored their behavior using video cameras. At the end of each experiment (shown here), the sea urchins were collected and returned to the laboratory, where marine biologists looked for any physiological changes that may have resulted from their exposure to slightly more acidic seawater.