A novel approach for the study of North Sea drill cuttings accumulations: the combined use of an ROV and benthic lander for in-situ measurements

Two benthic lander systems were used as part of a project investigating the geochemical characteristics of a North Sea drill cuttings pile. Complications associated with deploying sampling gear in close proximity to the platform required an innovative technique to obtain the necessary measurements. To achieve this goal, two deep-sea autonomous free fall vehicles (benthic landers) were adapted for deployment and transport by remotely operated vehicle (ROV). The landers were fitted with a microelectrode profiling system for obtaining high-resolution oxygen, sulphicle and pH profiles, and a rig to deploy gel probes into the sediment to examine dissolved trace metal profiles within the cuttings pile. The use of an ROV for deployment of the landers enabled the simultaneous collection of data within a defined spatial context while providing real-time visual feedback of the landers operating on the seabed. Eight deployments were made over 5 days, totalling over 100 hours of sampling time. The successful deployment and retrieval of the instrumentation, the quality of data obtained and the limited disruptions to the ongoing ship operations demonstrate the value of the lander system as an efficient and versatile tool for in situ biogeochemical investigations in areas associated with sampling and measuring difficulties such as North Sea drill cuttings piles.