Anthropogenic influence on sediment transport in the Whittard Canyon, NE Atlantic

• Nepheloid layers more turbid than natural or usual were identified in two branches of the Whittard Canyon in June 2013.
• VMS records showed high activity of bottom trawlers coinciding with the appearance of the layers.
• Molar C/N ratios indicate that sPOM from the layers is degraded hence likely resuspended material.
• The evidence persuasively suggests that bottom trawling is causing the increased turbidity.

Unusual peaks in turbidity were detected in two branches of the Whittard Canyon in June 2013. Enhanced nepheloid layers (ENLs) were defined as layers with concentrations of suspended particulate matter exceeding those of nepheloid layers typically observed in a given region. Here, ENLs had peaks in turbidity and elevated suspended particulate matter concentrations exceeding ~ 1 mg L− 1 with the largest ENLs measuring between ~ 2–8 mg L− 1. The ENLs measured ~ 100–260 m in vertical height and were detected in water depths of between 640 and 2880 m. Vessel Monitoring System data showed that high spatial and temporal activity of potential bottom trawling vessels coincided with the occurrence of the ENLs. Molar C/N ratios of the suspended organic material from the ENLs showed a high degree of degradation. Regular occurrences of such events are likely to have implications for increased sediment fluxes, burial of organic carbon and alteration of benthic and canyon ecosystems.