Limited knowledge of the taxonomy, biogeography and natural history of deep sea communities prevents accurate assessment of the risk of species extinctions from large-scale mining. Data acquired from the abyssal North Pacific and North Atlantic suggest that deep-sea ecosystems may be adversely affected by mining operations on decadal time scales. In 1978, a dredge aboard the Hughes Glomar Explorer, operated by the American mining consortium Ocean Minerals Company (OMCO), made a mining track at a depth of 5000 meters in the nodule fields of the CCFZ. In 2004, the French Research Institute for Exploitation of the Sea (IFREMER) conducted the "Nodinaut" expedition to this mining track (which is still visible on the seabed) to study the long-term effects of this physical disturbance on the sediment and its benthic fauna. Samples taken of the superficial sediment revealed that its physical and chemical properties had not shown any recovery since the disturbance made 26 years earlier. On the other hand, the biological activity measured in the track by instruments aboard the manned submersible bathyscaphe "Nautile" did not differ from a nearby unperturbed site. This data suggests that the benthic fauna and nutrient fluxes at the water–sediment interface has fully recovered.