Title : Role of picophytoplankton in the carbon cycle of the northern Indian Ocean

Abstract

Picophytoplankton are vital drivers of marine biogeochemical cycles and serve as indicators of ocean productivity, ecosystem health, and climate change. As the smallest single-celled phytoplankton, they play a crucial role in ocean ecosystems, being globally recognized as major primary producers and significant contributors to the oceanic carbon stock. Despite their ecological importance, their role is often underestimated, particularly in the northern Indian Ocean—an oceanic region characterized by high environmental variability and dynamic biogeochemical processes. In this seminar, I will present the results that aimed to quantify the abundance and carbon biomass of picophytoplankton and to assess the influence of regional physicochemical parameters on their spatial distribution and ecological role in the northern Indian Ocean. Our findings demonstrate that the contribution of picophytoplankton carbon biomass to the total particulate organic carbon (POC) pool was substantial in both the Arabian Sea and the Bay of Bengal. This underscores their significant, yet often overlooked, role in supporting the regional biological pump and influencing carbon fluxes.

Title : Investigating Lunar Subsurface Water Ice through Neutron Leakage and Gamma-Ray Continuum Flux

Abstract

Lunar volatiles, including water ice, are considered to be preserved in cold traps or buried beneath the surface layer near the poles. Understanding their distribution and abundance is critical for advancing knowledge of lunar evolution and for supporting future exploration activities. Neutron and gamma-ray spectroscopy provide key tools for this purpose, as subsurface hydrogen abundance can be inferred to depths of up to 1 m from measurements of neutron leakage flux and gamma-ray continuum flux from the Moon. In this seminar, I will discuss the lunar leakage neutron and gamma continuum flux induced by galactic cosmic rays interacting with the lunar surface, as well as their dependence on subsurface hydrogen abundances, using Monte Carlo simulations. The effects of temperature and compositional variation on neutron leakage flux are examined. The sensitivity of the leakage neutron intensity to the depth profile of subsurface water ice within the top 1 m of soil will also be discussed.