Leg 2 of DISCOL cruise underway

News date: 
August 31, 2015

With Leg 1 of the SO242 cruise complete, Leg 2 is now well underway in the Peru Basin. The German research vessel RV Sonne will spend two months in the Peru Basin revisiting the site of a seafloor disturbance experiment that was carried out by German researchers in 1989. The purpose is to assess potential impacts of the mining of manganese nodules on the deep-sea ecosystem, by re-surveying and sampling a site known as DISCOL (DISturbance and re­COLonization experiment), where the seafloor was deliberately ploughed in order to be able to monitor how the local ecosystem reacted and if it could recover.

During Leg 1 (SO242/1; 28 July - 25 August 2015) the entire disturbed area was mapped for the first time using AUV-mounted visual and acoustic techniques to assemble a complete habitat map. High-resolution side scan and multibeam data was acquired to precisely locate and image the plough marks on the seafloor, which are still clearly visible after 26 years. Sediment samples were collected using TV-guided equipment inside and adjacent to the plough marks, and at sites where the original sediment plume generated by the plough has deposited sediment. Initial analysis indicates that very little has changed in the area since the last survey 19 years ago.

During the second leg of the cruise (SO242/2; 28 August - 1 October 2015), research and sampling will focus on determining the composition of benthic communities (mainly mega-, meio-, and megafauna) and measuring ecosystem functions (biogeochemical processes, transfer of matter and energy in food webs, ecotoxicology). In addition, observations of the physicochemical characteristics of seafloor habitats and the overlying benthic boundary layer will be carried out.

As before, the team on board the RV Sonne will be keeping a cruise blog at www.oceanblogs.org/eadsm