The environmental consequences of deep-sea mining have been a matter of thorough research since the first pilot mining tests in the 1970th. Despite numerous efforts by the engineering and the scientific community, the technical means for in-situ observation and control as well as the possibilities for onboard or laboratory investigations vary greatly and fail to assist to answer these questions satisfactorily. Therefore, in the frame of the "German Interdisciplinary Deep-Sea Protection (TUSCH)"-programme special subprojects were launched to make new attempts to answer the above mentioned questions. This contribution summarizes the results from these investigations. By means of a new sediment sampler especially developed for this purpose, large volume, undisturbed cores were recovered, which allowed the necessary geotechnical investigations. The results indicated that the moveable sediment layer thickness barely surmounts the nodule diameter, that only a fraction of the recent sediment layer will he resuspended and form a cloud, that the near-bottom tailings will be caught by the wake flow of the miner, that most of the resuspended material will rapidly aggregate and resettle relatively fast, and that the chemical changes are negligible.
The environmental consequences of deep-sea mining have been a matter of thorough research since the first pilot mining tests in the 1970th. American, French, Japanese, Chinese, and German government and commercial organizations (Backer et aI., 1980; Burnett, 1991, Cruickshank, 1882, 1983; Desbruyere et aI., 1985) carried out a number of environmental impact assessment studies concerning the physical, chemical and biological changes which oceans might experience from manganese nodule mining. Despite all scientific and financial efforts executed by the scientific and the commercial communities, the technical means for in-situ observation and control as well as the possibilities of onboard or laboratory investigations were widely inappropriate so far to help to answer these questions satisfactorily.