- Dona Paula, Goa, India.
- +91-0832- 2450327
- iiosc2020[at]nio[dot]org
| Abstract Submission No. | ABS-2022-05-0127 |
| Title of Abstract | Sources and nature of particulate matter in sediment traps: a comparison between the Arabian Sea and the Bay of Bengal |
| Authors | Kurian, S*, Shenoy, D.M, Kabeer, M, Karapurkar, S, Khandeparkar, R, Krishnendu, P, Megha, D, Apsara, P.V., Harshada, K, Naqvi, S.W.A |
| Organisation | CSIR-National Institute of Oceanography, Goa |
| Address | CSIR-National Institute of Oceanography, Panaji, Goa, India Pincode: 403004 Mobile: 9423889319 E-mail: siby@nio.org |
| Country | India |
| Presentation | Oral |
| Abstract | Sediment traps are widely used to study particles sinking through the oceanic water column and provide information about the sources and nature of particulate matter. These particles (marine snow, fecal pellets, macroaggregates) consist of intact and remineralized biogenic and lithogenic material. Earlier studies have shown that the downward flux depends mainly on surface processes such as primary production, which varies seasonally and inter-annually. As a part of the SIBER-INDIA program, we had deployed a mooring in the Arabian Sea (AS; 17°N, 68°E) and Bay of Bengal (BoB; 18°N, 89°E) consisting of sediment traps at three depths (shallow: 600m, 480m, middle: 1200m, 1070m and deep: 3000m, 1600m) respectively. Here we compare the data of BoB sediment traps collected during 2011-12 with the AS traps collected in 2012-13. In both AS and BoB, middle and deep traps collected more material (>300 mg/m2/day) during the fag end of the southwest monsoon compared to shallow ones, probably due to lateral advection or scavenging of particles. Carbonates are the dominant component, ranging between 36 and 41% (avg.) in the AS and 14.6 and 21% (avg.) in the BoB. The high percentage of lithogenic flux (~50%) in the BoB traps is possibly due to the heavy discharge of suspended sediments through fluvial input. Organic carbon (Corg), total nitrogen (TN) contents and total hydrolyzable amino acid (THAA) concentration decreases with increasing water depth. This decreasing trend is possibly due to the decomposition of labile organic constituents in the sinking material while passing through the water column. The Corg and TN contents were higher in the AS (6.6 - 12.2%; 0.8- 1.5%) compared to BoB (4.6 - 9.3%; 0.7 ⿿ 1.1% respectively). δ15N is heavier (6 - 6.6 ⿰ avg.) in the AS than that of BoB (2.7 - 3.3⿰ avg.). Denitrification in the AS leads to a significant enrichment of 15N, whereas input from large rivers depletes 15N in the northern BoB. Though the Arabian Sea is more productive, opal flux is more in the BoB traps probably due to the higher ballast effect in the BoB. The opal % varied between 8.3 and 12.3 % (avg.) in the AS whereas it varied between 21.3 and 23.2% in the BoB. While our results are comparable with the earlier Indo-German collaborative sediment trap program carried out in the 1980s, long-term monitoring of sinking flux is essential for assessing the changes in source and nature of the particulate matter in the present scenario of global change. |