The IOM comprehensive environmental program began in 1994 and consists of two main phases: pre-contract phase (1994 ‐ 2000) and research which has been carried out after signing the contract for exploration with the International Seabed Authority (2001 – at present).

Pre-contract phase. Baseline studies along the so‐called reference transect cutting through a considerable portion of the IOM claim area (over 330 km long) were conducted. The in situ Benthic Impact Experiment (IOM BIE) was run in 1995 followed by monitoring of the impact site in 1997 and 2000. During this phase a particular emphasis was given to gather data on physical and chemical oceanography; a total of 14 CTD stations situated along the Reference transect were surveyed twice, in 1994 and 1995; near bottom currents were measured over the 8‐months period by four moorings. For the first time, macrobenthos in the IOM claim area was studied in 1994 and 1997, and taxonomic identification, densities, and vertical distribution were analysed at 7 sediment cores; epibenthicmegafauna in nodule‐bearing and nodule‐free areas were examined on the base of bottom photographs taken along the transects with common lengths about 70km.

To assess potential environmental effects of nodule mining, IOM carried out in July 1995 BIE experiment involving scaled stressing to benthic communities and their habitat. The disturbance was affected by a Deep Sea Sediment Re-suspension System towed on the bottom along 14 tracks laid out within a 2 x 1.5 km test site. Meiobenthos, selected as a key biotic variable with which to assess effects of disturbance, was sampled at stations distributed randomly in three areas identified as control, impacted, and re‐sedimentation areas. Twice, in April 1997 and in June 2000 meiofauna was again analysed using the same sampling strategy. The entire IOM BIE program resulted in accumulation of an extensive data set on the abundance and composition of the meiobenthos; importantly, a very high biodiversity, at the genus level, of the two major taxa, nematodes and harpacticoid copepods was demonstrated.

Contract phase. The new phase ofthe IOM environmental project has started since 2001,after signing a contract with the ISA for exploration for polymetallic nodules.

According to the contract’s standard clauses, the goal of this study is to gather environmental baseline data necessary for establishment of the environmental baselines for  assessing the likely effects of mining activities on marine environment.

IOM carried out three cruises in 2001, 2004, and 2009, and sediment samples have been retrieved by box-corer from a total of 311 stations; the follows parameters of sediments: pH, Eh, grain size, bulk density, water contents, heavy metals, opal and organic matter were analyzed at specific layers; pore waters from the same sediment layers were also examined for nutrients and metals. Epibenthicmegafauna assemblages and its biogenic traces (Lebensspuren) was analysed based on two sets of images taken in 2001 and 2009 by deep towed camera along 20 transects over a total of 607 km distance. The composition of the megafauna showed that the main part (94%) is consisted of 6 taxons (Xenophyophorida, Porifera, Ophiuroidea, Actiniaria, Echinoidea, Holothuroidea); nevertheless, the nodule‐free seafloor was characterised by a less abundant megafauna (averaging 274 inds/ha) than that inhabiting the nodule‐bearing areas (averaging 355 inds/ha). Analyses of abundance and composition of the macrofauna collected from 11 stations during IOM’2009 cruise are in processing. Pursuant to the ISA environmental recommendations and guidelines IOM is currently engaged in classification and systematization of all available data and information on marine environment in exploration area, using the 6 groups of parameters: ocean physics, ocean chemistry, sediment properties, biological communities, bioturbation, and sedimentation.