01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0129 |
| Title of Abstract | Embarking on a diatom odyssey: Insights from a systematic study across pelagic zones in the equatorial and south tropical Indian Ocean |
| Authors | Ankur Sharma*, Jagadish Patil , Pranoy Paul, Aparna MOL TA, Samir Damare |
| Organisation | CSIR-NIO, AcSIR |
| Address | SAB-2 , NIO COLONY , DONA PAULA , PANAJI Panaji, GOA, India Pincode: 403004 E-mail: Anvish.sharma12@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Diatoms, prominent microbial eukaryotes, contribute ⿼40% of marine primary productivity and are central to the Biological Carbon Pump. Yet, their ecological dynamics and mechanistic drivers beyond the euphotic zone (~200 m; ~4.5% of ocean volume) remain poorly understood despite their role in carbon export. This first systematic, depth-resolved survey of >100µm diatom communities across epipelagic, mesopelagic, bathypelagic and abyssopelagic layers in the understudied Equatorial (EIO) and South Tropical Indian Ocean (STIO), incorporating gradients of island proximity and bathymetry. Diatom abundance declined steeply (85⿿95%) from epipelagic to bathypelagic and by up to 99% in the abyssopelagic; nevertheless, mesopelagic species richness was retained (36⿿270% of surface values), supporting the existence of deep-sea ⿿seed banks and functional diversity reservoirs. Strong morphological filtering favours cylindrical frustules in deeper zones, optimising sinking and export potential. Community structure was regionally distinct: EIO-A1 (shallower, 1,500 m) hosted higher diatom abundance than EIO-A2 (4,000 m) despite similar proximity to land, implicating bathymetric enhancement of nutrient advection and the island mass effect as key assembly drivers. Remarkably, in the STIO-A, weak upper-ocean density stratification facilitated rapid sinking and a mesopelagic biomass ⿿trap, producing higher mesopelagic than surface abundance⿿a pattern not observed in regions with stronger density gradients. Distinct taxa dominated different zones (e.g., Climacodium frauenfeldianum epipelagic, Chaetoceros coarctatus bathypelagic, Asterolampra marylandica abyssopelagic), indicating niche partitioning along depth and trait axes. These findings reveal a crucial interplay among frustule architecture, hydrography, and loss processes (grazing, degradation) in structuring diatom-mediated carbon export across pelagic strata, advancing mechanistic understanding of vertical microbial ecosystem function. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Diatom sinking, Seed bank, Density, Bathymetry, shapes |
| For Awards | yes |
| Date Of Birth | 18-06-1997 |
| ECSN Registration Number | IIOE2-ECSN-0116 |