Measurements of Suspended Sediment Concentration in the Deep-Sea – Challenges Based on a Previous Measurement Campaign and How Those Challenges Might be Addressed
Type:
Presented during:
WODCON XXIII - Dredging is changing - The Practice. The Science. The Business.
Authors:
N. Crossouard, J. Taylor, M. Lee
Abstract
"Deep-sea mining can involve the extraction of poly-metallic nodules, ferromanganese crusts and sulphide deposits from the ocean floor and transportation of the mined material to the water surface. The mining of these resources (and potential discharge of unwanted material also excavated from the seabed) will potentially result in adverse ecological effects arising from the formation of sediment plumes that could deposit fine sediment on sensitive species. Identifying the behaviour of such sediment plumes is therefore a critical part of designing deep-sea mining operations that minimise impacts on ecology. Monitoring of the plumes has particular importance given the very low background levels of suspended sediment concentration that the sensitive receptors often exist in. In coastal waters sediment plume characterisation is traditionally carried out using optical (optical backscatter sensor (OBS)) and acoustic (ADCP) technology. Here we present some of the challenges of performing sediment plume monitoring in the deep-sea and how those challenges may be addressed. The information presented is based on experience gained during a previous sediment plume monitoring campaign undertaken on the Tropic Seamount, 550km SSW of the Canary Islands. The monitoring undertaken included the deployment of an ADCP and OBSs in water depths of >1000m."
Keywords: suspended sediment concentration, deep-sea mining, turbidity, sediment plume, monitoring