Summary of Abstract Submission

Abstract Submission No. IO50-02-0013PresentationPoster

SOURCES AND NATURE OF PARTICULATE MATTER IN SEDIMENT TRAPS AT BAY OF BENGAL TIME SERIES

Siby Kurian*1, Pratima M. Kessarkar1, Supriya G. Karapurkar1, Damodar M. Shenoy1, Chandrasekhar Rao1, Lina L. Fernandes1, Mangesh U. Gauns1, S.W.A. Naqvi1

1 CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India

ABSTRACT :

Sediment traps are widely used to study particles sinking through the oceanic water column. Earlier studies have shown that the flux depends mainly on surface processes such as primary production and varies seasonally and inter-annually. As a part of the SIBER-INDIA programme, we have deployed a mooring in the Bay of Bengal (18N, 89E) consisting of sediment traps at three depths (shallow (480 m), middle (1070 m) and deep (1600 m)). We present here data on vertical flux, concentrations and isotopic composition of C and N, rock magnetic properties, clay mineralogy and geochemistry during 2011-2012. The middle and deep traps collected more material (upto 350 mg/m2/day) during the fag end of the south-west monsoon. Lithogenic flux accounted for ~50% of the total flux whereas carbonate flux was < 20%. Average C/N ratio varied between 9 and 10 with 13C values in the range of -220.5 showing largely marine origin of the particulate organic matter. The 15N values were lower (<3) in the shallow and middle traps increasing to ~5 in the deep trap during Sept-October. The magnetic susceptibility ranged between 3 and 48 x 10-8 m3/kg with smectite and illite being dominant minerals. Average concentration of Mn was low in shallow trap (837 ppm) and highest in the deep trap (2033 ppm). REEs also followed the same trend. The results suggest changes in the source of suspended particulate material with depth and season.