The Arctic Ocean is undergoing rapid changes to the physical environment as a consequence of anthropogenically induced climate change. These changes are particularly apparent in the Barents Sea, which is considered a hotspot for Arctic warming. Declining sea ice cover has been accompanied with an increased intrusion of Atlantic water into the shelf sea. Such changes have resulted in larger areas, and longer periods of open water during the summer months, leading to increases in annual net primary production. I investigated the resulting effects of such changes on microbial communities and organic carbon cycling in the Barents Sea by combining biogeochemical, molecular and Earth observational techniques. Firstly, a novel dataset on microbial phosphorus utilisation revealed significantly faster and tighter phosphorus cycling associated with Atlantic, opposed to Arctic, phytoplankton communities. Future increasing Atlantic influence, could lead to a greater importance of phosphorus, rather than nitrogen, in mediating primary production. Secondly, I provide the first direct experimental evidence of an intense under ice diatom bloom in the Eurasian Arctic sector. I combined ship-based rates of primary production with satellite observations to estimate that under ice blooms could potentially account for up to 32% of regional primary production. Finally, investigations into the balance between autotrophy and heterotrophy revealed that bacterial production is strongly coupled to phytoplankton production. The supply and composition of phytoplankton derived organic substrates appeared to govern heterotrophic community structure. These combined results suggest that organic carbon cycling in the Barents Sea is highly sensitive to the changing physical environment. Further work is required to reveal the full extent and significance of under ice blooms, and unravel the functional composition of dissolved organic carbon. This will enable the scientific community to comprehensively understand and realistically predict the biogeochemical and ecological consequences of climate change in this highly productive shelf sea environment.
Date of Award | 22 Mar 2022 |
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Original language | English |
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Awarding Institution | |
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Supervisor | Fanny M Monteiro (Supervisor) & Dan Lunt (Supervisor) |
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The effects of changing sea ice conditions on microbial production and community composition in the Barents Sea
Downes, P. P. (Author). 22 Mar 2022
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)