Photo mosaic marks successful end to expedition

Scientists return to ploughed seafloor to assess condition of terrain

Preparing the AUV ABYSS for a dive. During the expedition, the unit has delivered accurate maps and photos taken at more than 4,000 metres depth (B.Barenbrock, GEOMAR).

Imagine gigantic unmanned crawler vehicles moving along pre-programmed paths on the seafloor in search of manganese (polymetallic) modules - This is the future of deep-sea mining.

As intriguing as this image may be — and before such scenarios become commonplace — we need to first anticipate how mining activities would affect the ecosystem of the seafloor, and how long would it take for the terrain to heal itself.

These were some of the questions addressed by "JPIOceans – Ecological Aspects of Deep-Sea Mining", the joint European research project that brought together scientists from Germany, Portugal, the United Kingdom, Belgium and the Netherlands to the eastern equatorial Pacific.

Congregating on board the German research vessel SONNE, they created one of the largest high-resolution photo mosaics of the ocean floor, using the autonomous underwater vehicle AUV ABYSS.
Part of the 4,000m deep Peru Basin, this particular portion of the seafloor was special. This was where in 1989, German scientists ploughed about 2.5 square kilometres of where manganese nodules emerged on the ocean floor. It was part of the DISturbance and re-COLonization experiment (DISCOL), which sought to study the long-term impact of such activities in the deep sea and how quickly the affected ground would be repopulated.

One of the several 100,000 photos of the seafloor, taken by the AUV ABYSS. The plough marks from 1989 can be seen alongside the tracks of a subsequent sampling in the centre.

The scientists then returned to the site in 1992 and 1996 to monitor the ploughed seafloor. And, most recently, in August 2015.

"Fortunately, the deep-sea technology has improved a lot since the 1990s," said cruise chief scientist Professor Dr Jens Greinert of the GEOMAR Helmholtz Centre for Ocean Research Kiel. As a result, the scientists were able to utilise new technologies that were not available for the previous expeditions.
On the 2015 expedition, the scientists used autonomous underwater vehicles like the AUV ABYSS, which could follow pre-programmed courses for more than 20 hours, mapping the seabed with multibeam echosounders and side-scan sonar. Several thousands of photos had been taken by the AUV ABYSS a few metres away, using a newly developed lighting technology. These were the photos that made up the photo mosaic of the seafloor in unprecedented high-resolution clarity.

Manganese module from the deep-sea (KOELLE, Wikipedia)

The AUV also allowed the scientists to maximise their time. While it worked autonomously underwater, the research vessel was able to take samples at another location.  

Now, armed with the newly collected data, maps, photos and samples, the scientists are back in the labs to conduct their analysis. The plough tracks from 1989 were still visible and the region had not yet been colonised. However, the images captured shows that several decimetres from the plough tracks, normal deepsea life exists.

"This expedition proved that the deep sea is not an area that is beyond monitoring. Mining activities can be monitored efficiently, the technology is already available," said Professor Greinert.
 
Further information: www.geomar.de