Environmental Study

Environmental Study

DORD has been conducting environmental surveys as part of its exploration activities for polymetallic nodules in its license area. The purpose of these surveys is to acquire environmental baseline data necessary to assess environmental impacts arising from mining activities. While the study of mining systems by DORD is currently at the conceptual design stage, specific study items and methods are in accordance with ISA environmental guidelines. To this day, sediment and seawater sampling has been implemented, as well as a mooring system has been installed for one year to measure the current direction and velocity. Additionally, sampling by utilizing a vertical multiple plankton sampler (VMPS) and observation of megafauna on the seafloor by taking photographs have been conducted. To optimize survey cruises, resource surveys for estimating polymetallic nodules and environmental studies are sometimes carried out on the same survey cruise.

Sediment sampling at depths of 5,000 m is implemented by using a spade-type box corer (BC) or a multiple corer (MC). While unloading and raising the sampling equipment, the vessel may shake and affect the quality of the sample. Therefore a great attention is being paid to the weather and the sea conditions while surveys are carefully being conducted . While the survey equipment is being unloaded, a pinger attached to the equipment is used to monitor the tension of the wire from which the equipment is hanging and how close it approaches the bottom surface. When polymetallic nodules are brought up with the sediment, these are also used for analysis.

For sediment samples, besides chemical component measurements, microorganisms are also examined. After sieving the sediments into individual sizes from one to several centimeters on board, the number and type of organisms are examined by its size. Some parts of the deep seafloor organisms are found in common with organisms found on land. However, as sampling of benthopelagic organisms sometimes require certain expertise, we sometimes cooperate with universities or specialized organizations.

An equipment called a rosette sampler (RO) is used for seawater sampling. This instrument is equipped with several sampling bottles, concentrically arranged, and the lid is closed and sampled at the targeted water depth for each bottle. The RO is equipped with a sensor called a conductivity, temperature, and depth profiler (CTD), and it acquires data such as water depth, temperature, and conductivity in real time. The signal to close the lids is operated on board while watching the depth data from the CTD.

Before DORD signed its exploration contract with the ISA, the Metal Mining Agency of Japan (MMAJ, currently named as the Japan Oil, Gas and Metals National Corporation (JOGMEC)), carried out a disturbance experiment in the Japan Deep-Sea Impact Experiment (JET) area in 1994. This experiment was conducted in order to evaluate the environmental impacts caused by the seabed disturbance associated with mining operations. A benthic disturber called a deep-sea sediment resuspension system (DSSRS), which simulates a nodule collector that disturbs the seafloor sediment, was utilized. The disturbed area, volume, and re-sedimentation of disturbed sediment, as well as changes in the types and populations of organisms were monitored. Since the exploration contract entered into force, DORD has been conducting monitoring surveys.