Phytoplankton-nutrient interactions in the upper ocean

海洋覆盖了约71%的地球表面，并强烈影响着全球气候。浮游单细胞藻类（浮游植物）通过改变海洋的碳平衡在改变地球气候方面发挥着关键作用，这对大气中的二氧化碳浓度有直接影响。这些光合生物通过光合作用吸收营养物质（如碳、氮、硅、磷），并在死亡和分解后将其送回海水，从而控制海洋和大气中的二氧化碳水平。浮游植物的生理也会影响海洋食物网的营养转移，从而影响鱼类和海洋哺乳动物的生存。

The ocean covers about 71% of the earth's surface and strongly affects global climate. Floating unicellular algae (phytoplankton) play a critical role in modifying the earth's climate by changing the carbon balance of the ocean, which have a direct impact on atmospheric carbon dioxide concentrations. These photosynthetic organisms take up nutrients (e.g. carbon, nitrogen, silicon, phosphorus) through photosynthesis and return them back to seawater after death and decomposition, thereby controlling the level of carbon dioxide in the ocean and atmosphere. Phytoplankton physiology can also affect nutrient transfer along marine food webs with consequences for the survival of fish and marine mammals. High-latitude oceans are experiencing the most dramatic climatic variations due to global warming. Predicted changes (e.g. in sea ice cover, circulation patterns, water column stratification, temperature, dissolved carbon dioxide, nutrient supply) will impact marine ecosystem structure and function by affecting phytoplankton productivity at the base of the biological system. Therefore, it is critical to evaluate phytoplankton responses to ocean warming and acidification in subarctic and arctic seas. This research program examines the links between phytoplankton physiology and nutrient cycling in the ocean. Studies will be conducted in the laboratory and on oceanographic research cruises to the subarctic Northeastern Pacific and western Arctic Oceans, and utilize interdisciplinary techniques. Specifically, I will advance my research by studying (1) biogenic silica production and silicon isotopes, (2) the balance between planktonic calcification and photosynthesis, and (3) phytoplankton elemental composition. I will explore the sensitivity of nutrient acquisition in marine phytoplankton to nutrient limitation and changing environmental conditions. Results will shed new light on the factors affecting the productivity of marine phytoplankton, and improve our understanding of present and past nutrient cycles, carbon export and food web dynamics in high-latitude marine waters.