Close this search box.

Santona Khatun

Santona Khatun

Home Institution: Institute of Earth Surface Dynamics, Lausanne

Host Institution: Stockholm University

Duration of stay (months): 5

Objectives: Offshore freshened groundwater (OFG) is known as an unconventional water resource in the continental margins all over the world having an approximate volume of 0.072% water on Earth1,2. The existence of these freshened aquifers may play an important role in the hydrological cycle, however, is often ignored by massive sea water and conventional terrestrial groundwater hydrogeology. Even though the study of understanding OFG geometry in coastal regions has been growing rapidly3,4, little is known about the biogeochemical impact on Arctic fjords ecosystems in response to global climate change.
Changes in climate have long been recognized in the high-Arctic marine sediment of the Svalbard fjords where polar and/or glacier meltwaters are increasing and influencing the physical, chemical, and biological functioning of the fjord sediment ecosystems5,6. As the fjords are highly exposed to global climate change and ocean warming, their impact on OFG in Arctic fjords is inevitable. Therefore, the objectives of my research, in collaboration with the Ocean and Mud group of Stockholm University (Prof. Wei-Li Hong), are to clarify the biogeochemical impact of OFG interaction in Arctic fjords ecosystems.
Specific objectives are:

  1. To identify the presence and impact of OFG on nutrient dynamics in Arctic fjords.
  2. To evaluate the future projected changes in biogeochemical cycles related to OFG.

Summary of the work: The main goal of our current collaboration is to obtain and integrate detailed knowledge about the biogeochemical impact of OFG in the Arctic fjords and its connection to marine nutrient cycling. Only a part of the analysis is completed, the results helped us to predict the effect of OFG on marine habitats as well as altering ecosystem functions. Microbial DNA analysis was performed for the sediment samples collected from Superstation-2 (SS2), Superstation-5 (SS5), and Superstation-6 (SS6) in the Mineral Vivant Lab, University of Lausanne to understand the presence and variation of microbial communities among cores collected from different superstations at Svalbard fjords. For SS6, we measured the DNA yield for two cores at the 2-4cm depth where we observed the high microbial abundance in both cores. Biogeochemical properties of the pore water and sediment samples were analysed using standard and accredited methods at the Ocean and Mud lab, at Stockholm University. We analysed the sediment cores collected from SS6 and observed high TC and TOC content in the upper layer which tended to decrease with the depths minimising around 8cm (Core 1) and 20cm (core 2) depths indicating high microbial abundance in the upper layer. Interestingly, the δ13C TC values of Core 1 were likely to increase from −20 ‰ (1 cm) to −17 ‰ (0-8 cm) and the δ13C TOC values remained unchanged. While in Core 2, the δ13C TC value increased to −14 ‰ (19 cm) from the surface zones. The combined results of geochemical and biological information will help to understand whether this unconventional water source leads to changes in carbon balance in Arctic areas by enhancing land-ocean connectivity.