About the project
Many areas of our oceans are extremely nutrient poor, so phytoplankton have evolved diverse ways to support photosynthesis and enhance nutrient acquisition in these regions. This project will examine how diatoms use photosynthetic enzymes to manipulate their cellular microenvironment and increase the availability of nutrients.
Diatoms are a major group of marine phytoplankton that are responsible for an estimated 40 % of photosynthetic carbon fixation in oceans, although their productivity in many areas is limited by the availability of nutrients such as nitrogen, phosphorus and iron. Diatoms therefore use specialised mechanisms for both carbon and nutrient uptake, although these remain poorly understood.
The enzyme external carbonic anhydrase allows diatoms to enhance the capture of carbon dioxide and support high rates of photosynthesis. External carbonic anhydrase activity strongly influences pH and carbonate chemistry around the cell (Chrachri et al 2018), which may also influence the acquisition of other nutrients, particularly iron.
This project will examine whether diatoms actively exploit photosynthetic activity to enhance iron uptake. It will address the following questions:
- Do diatoms manipulate cell surface carbonate chemistry during photosynthesis to enhance iron acquisition?
- Does external carbonic anhydrase interact directly with mechanisms of iron uptake?
- Is this mechanism exploited by natural diatom communities in iron-limited environments?
Molecular biology approaches available in the model diatom Phaeodactylum tricornutum will examine how external carbonic anhydrase contributes to growth and photosynthesis under iron-limited conditions. Environmental datasets from the iron-limited Southern Ocean will be examined to identify whether these molecular mechanisms play an important role in natural diatom communities.
The project will characterise novel aspects of nutrient uptake in marine phytoplankton that will allow us to understand their growth and better predict how they will respond to shifting nutrient regimes in under future climate scenarios.
You will also be supervised by organisations other than the University of Southampton, including Dr Glen Wheeler and Dr Matthew Keys from Marine Biological Association.
