ABSTRACT:

Significant results have been obtained from, an extensive database generated on water column and benthic baseline conditions. Seafloor surveys have resulted in selection of suitable test and reference areas, and in identification of site for benthic impact experiment. Evaluation of impact of simulated disturbance in the benthic environment shows vertical mixing of sediment, lateral distribution of particles, changes in geochemical and biochemical conditions as well as reduction in biomass in the benthic environment. The results obtained are useful in determining the indicator parameters and standardising the methods for assessment of effects of large scale mining.

INTRODUCTION

Environmental impact studies have gained importance due to the concern for possible effects of large scale mining on marine environment. In view of the proposed implementation of certain regulations for environmental effects of deep-sea mining to the potential contractors (ISA, 1998), these activities have gained momentum in Various research groups have simulated disturbance on the seabed using mechanical and hydraulic devices (Foell et. aI, 1990; Trueblood, 1993; MMAJ, 1994; Tkatchenko et al., 1996) to study the effects on different environmental conditions in potential mining areas. recent years.

TARGETS ACHIEVED
1.Evaluation of baseline conditions in the study areas (1995–1997)
Benthic conditions

Close grid sampling and observations on various environmental parameters in 5 selected areas, has lead to detailed baseline data on benthic conditions. Two sets of study areas (such as AI, Tl, Rl; and T2, R2) were selected from multibeam data and nodule abundance in the Central Indian Basin (Fig. 1). These areas were studied in detail for sediment characteristics, nodule distribution, seafloor bathymetry. and sediment thickness for identification of test and reference sites. Seabed samples were also analysed to establish baseline conditions of geochemical,. stratigraphic, geotechnical, benthic biomass and microbiological status of the area.

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