Dissertation Title: Polar Flow: Investigating polar phytoplankton's functional biodiversity using Imaging Flow Cytometry and artificial intelligence.

Master's Thesis Title: Developing a Novel Methodology to investigate Diatom Silicification in the Eurasian Basin of the Arctic Ocean using Imaging Flow Cytometry and PDMPO

natasha.bryan@awi.de 

Alfred Wegener Institut
Am Handelshafen 12
27570 Bremerhaven

E-1015

Phytoplankton communities living inside and below sea ice in the Arctic and the Antarctic arefacing rapid changes due to ongoing climate change. Light and nutrient availability as well as shifts in grazing lead to changes in biodiversity. However, we still lack quick methods to assess simultaneously the abundance of certain species and their physiological traits at a single cell level. Thus, the impact of changes in phytoplankton biodiversity on specific ecosystem processes, such as nutrient cycling, is still understudied. 

Since polar phytoplankton and sea-ice algal communities are usually dominated by diatoms (which take up silicic acid to grow) and flagellates (autotrophs or heterotrophs), understanding the silicification degree and the role of mixotrophs in these communities is crucial to predict how shifts in biodiversity will affect ecosystem services in the polar regions. 

The overall objective of Polar-Flow is to develop a high-throughput methodology to assess biodiversity, silicification and mixotrophy in polar phytoplankton using imaging flow cytometry, fluorescent tracers, and artificial intelligence classification analysis. This methodology will be applied to answer the following research questions: Which AI classification method is better suited to taxonomically classify polar phytoplankton composite images obtained with the multispectral Imaging Flow Cytometer? How do Arctic phytoplankton communities differ from Antarctic communities in terms of their species composition, silicification degree and mixotrophy percentage? Under which environmental conditions do mixotrophs thrive and how can this physiological plasticity help them adapt to ongoing climate change?