During both the baseline and the post-impact studies the seafloor was monitored with an OFOS (Ocean Floor Observatory System), consisting of two different units: an onboard unit and an underwater unit. The underwater unit was basically a metal frame, which contained video and photo cameras to study the seafloor visually. It was also equipped with batteries, a navigation transponder as well as lamps and flashes and was towed behind the ship a few metres above the seafloor. The onboard unit was used to control the correct operation of the underwater unit as well as to enable a first live-evaluation of the video material, on-command photography and in the end to store the data for further examination.
The large OFOS instrument package was lost during another research cruise prior to the third post-impact study (DISCOL 3) and was replaced by a smaller OFOS system called EXPLOS (Exploration System). However, the operation of the OFOS/EXPLOS deployments did not change and was also used during the SO106 cruise in 1996.
Over the course of the four different research cruises a total of 39 OFOS dives were performed successfully and over 30000 photographs and several days of video material were taken of the seafloor in- and outside the DEA. These data were mainly used to determine both the faunal composition and environmental conditions inside the DEA (DISCOL 1) and to monitor any changes during the post-impact studies (DISCOL 2 and 3, ATESEPP).
In preparation of the most recent post-impact study of the area in the course of the JPI Oceans Pilot Action “Ecological Aspects of Deep-sea Mining”, these images were digitalized and georeferenced to enable more detailed studies on the evolution of the faunal composition and the environmental changes within the ecosystem in the area of the DEA.