01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0123 |
| Title of Abstract | Unravelling the spatial variability in sedimentary phytodetrital flux in the central Arabian Sea: evidence from lipid biomarkers |
| Authors | Medhavi Pandey*, Haimanti Biswas, Daniel Birgel, Nicole Burdanowitz, Birgit Gaye |
| Organisation | CSIR-National Institute of Oceanography, Goa |
| Address | SR-16 PANAJI, Goa, India Pincode: 403004 E-mail: bhu.medhavi@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | The Central Arabian Sea, a tropical basin in the northwestern Indian Ocean, experiences seasonality in surface circulation, biogeochemistry and particle flux dynamics due to monsoon winds. High primary productivity, characterised by phytoplankton blooms and associated particle flux, occurs in its northern part (above ~15°N), due to summer monsoon-induced open-ocean upwelling and winter convection. This region also hosts a thick oxygen minimum zone (OMZ), which influences composition, export and preservation of sinking organic matter. This study examines sedimentary phytodetrital variability along a north-south transect (21-11°N, 64°E) in the central Arabian Sea, utilising lipid biomarkers and identifies the key factors governing organic matter export and preservation. Satellite data analysis revealed a clear north-south variability in sea surface temperature (SST) and chlorophyll concentrations. These trends are consistent with C37 alkenone-based SST, showing cooler waters (27.6±0.25°C) in the north and warmer SSTs (28.0±0.26°C) in the south. Lipid biomarkers indicate higher contributions from dinoflagellates throughout the transect, with dinosterol and dinostanol dominating over brassicasterol and alkenones, markers for diatoms and coccolithophores, respectively. Northern stations show the highest organic carbon (0.97±0.06%), nitrogen (0.087±0.018%), and biomarker concentrations (e.g., dinosterol: 12.81±6.30μgg⁻¹ TOC), but low cholesterol suggesting lower zooplankton. Siliceous microfossil analyses support these findings, with high diatom frustules (5.46±0.95ÿ10⁴valvesg⁻¹) and low radiolarian abundance (1.26±0.35ÿ10⁴individualsg⁻¹). Contrarily, in the south, low phytoplankton and high zooplankton biomarkers were observed, supported by the occurrence of fewer diatom frustules (3.26±1.08 ÿ104 valves g-1) and high radiolarian abundance (1.98±0.43 individuals g-1), respectively. This study thus utilises lipid biomarkers as a proxy of sedimentary organic matter to unravel the relative contributions of different plankton groups to export and preservation of organic matter in sediments in relation to surface processes. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Organic carbon, Phytosterol, C37 alkenone, Sediments, North Indian Ocean |
| For Awards | no |