ABSTRACT:

Deep sea sediments from Central Indian Ocean Basin (CIOB) were sampled from 10°.00" -10°.10" S latitude and 75°.55" -76°.05" E longitude for assessing the potential environmental impact of polymetallic nodule mining under the Indian Experiment (INDEX) during September 1996 and June-Sept 1991. Analyses were done for lipid, protein and carbohydrates, which comprise the labile organic matter (LOM), total organic carbon (TOC) and total bacterial counts (TC). Of the 5 variables tested, TC seemed to be relatively invariant. Analyses of variance (ANOVA) between grab and core samples showed that one could substitute the other for sampling only up to 10cm depth. Variability observed between samples for the two years could be due to temporal factors.· Paired Test between pre- and post-disturbance samples suggested that the above methods of sampling and variables like TC, protein and TOC could be used for monitoring disturbance.

INTRODUCTION

The Exploration for polymetallic nodules from the sea floor of Central Indian Ocean Basin (CIOB) started in 1981. An area of 150,000 km2 was allocated to India by UNCLOS with exclusive rights to carry out research and to explore this area for deposits in the subsequent years. Thus the Indian Deep-Sea Experiment (INDEX) was initiated in 1995, with the objective of predicting the environmental impact of mining in CIOB. The ecology of the bacterial and biochemical variables of CIOB (Area I and Ia) have been dealt in detail by Raghukumar et al and Nair et aI, (communicated). The use of different sample handling procedures greatly affects the microbial biodiversity (Rochelle et aI1994). Consequently, the choice of methods for sampling and analyses are of paramount importance for ensuing spatial and temporal comparison and monitoring. With this view in mind, we have re-examined the above data to evaluate a strategy for routine analyses in EIA studies in the deep sea.

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