Disputation: Cheshtaa Chitkara

Chitkara has followed the PhD programme at the Faculty of Engineering and Science at the University of Agder, with specialization in Natural Sciences, scientific field Coastal Ecology.

«Arctic marine microbial eukaryotes–Spatiotemporal drivers of community structure and ecological impacts of Atlantification»

Public summary:

The Arctic is changing rapidly, warming over four times faster than the global average. A key driver of this change is Atlantification—the northward push of warm, salty Atlantic water into the Arctic marine environment. This not only alters the climate but also impacts tiny yet vital organisms in Arctic waters: microbial eukaryotes. These microbes play diverse roles—some are producers using sunlight for photosynthesis, others are consumers feeding on these producers and other smaller organisms. Many are mixotrophs, switching between feeding and photosynthesis, especially useful during the dark polar night. Some are parasites or form mutual partnerships, and all are crucial to balancing the marine ecosystem and supporting the food web. My PhD investigates how these microscopic communities are changing over time and space in a warming Arctic. Using over a decade of data from different Arctic fjordsin Svalbard, Greenland and northern Norway, it focuses on two main questions: (1) how communities shift with the seasons (Seasonality), and (2) how they respond to warming events linked to Atlantification. Results show that sunlight and temperature are the main environmental drivers of eukaryotic microbial communities. Spring blooms characterized by an increase in growth of photosynthetic microbial eukaryotes, occurred in all studied fjords, but their timing didn’t always align with latitude. Summer blooms in especially warm years suggested that the system is already being affected by Atlantification. Although the communities show resilience, subtle but significant shifts were visible throughout the community data.

Opponent ex auditorio:

The deadline for the public to pose questions is during the break between the two opponents. Questions ex auditorio can be submitted to Disputation Chair Elna Svege