The Japan Deep-Sea Impact Experiment (= JET) was carried out in 1994 in the Pacific Ocean, to test the effect of artificial rapid deposition event, supposed to occur during commercial mining. As a part of JET, major chemical components of sediment in pie- and post-deposition events were measured. From the vertical profiles of chemical components in predisturbance, deposit material was estimated to be comprised of a lesser portion of organic carbon, nitrogen and calcium carbonate than the sediment surface on the sea floor. The results also demonstrate that the greater changes occurred in location near the disturbance and those were limited to the upper parts of the sediment.
Japan Deep Sea Impact Experiment (JET) initiated in the summer of 1994. This experiment was designed to evaluate the responses of benthic communities to an artificial rapid redeposition event, which was supposed to occur in commercial mining. Similar experiments have been conducted by Germany (DISCOL) and the USA (BIE) (Schriever, 1995, Tmeblood and Ozturgut, 1997). Although most studies have focused on the biological responses to the artificial impact, chemical properties of sediment have not been studied well. Organic material contained sediment is an important food source for many deepsea benthic fauna, particularly deposit feeders. A severe reduction of food source would cause a portion of organism to either die or lose the energy needed to reproduce, resulting in lower abundance (Jumars, 1981). In short, heterogeneity in sediment components indicates heterogeneity in the feeding environment for benthic organism and can therefore be positioned as an important background factor to understand temporal and spatial changes in benthic communities. The concentration of biogenic silica in top 1 cm layer was so high (~10%) that the sediment was classified as siliceous clay (Harada et al., 1995).