How do climate-driven shifts in phytoplankton communities influence carbon and nitrogen uptake and recycling along the west Antarctic Peninsula?

Project summary:
Biological carbon and nutrient uptake and recycling will be examined at the west Antarctic Peninsula in relation to climate-driven changes in phytoplankton biomass and species composition.

Background and rationale:
The west Antarctic Peninsula (WAP) has experienced significant atmospheric and ocean warming since the 1950s with a concurrent reduction in sea ice extent and duration. These trends have slowed since the 2000s, reflecting large natural variability superimposed on longer-term trends related to climate change.
Climate-driven changes in sea ice dynamics and upper ocean physics and chemistry have significant effects on primary production (PP), influencing phytoplankton bloom magnitude and species composition, with important consequences for the entire food web. PP and phytoplankton species composition regulate biological carbon and nutrient uptake, with major impacts on WAP shelf nutrient budgets, fluxes and air-sea exchange of CO2. The central objective of this PhD is to quantify the biological uptake of carbon and dissolved nitrogen forms under a range of conditions during the summer growing season at the WAP, and to determine how uptake may vary with climate-driven changes in phytoplankton bloom magnitude and composition. This will inform projections of future changes in WAP shelf biogeochemistry and ecosystem function as climate change proceeds.

Key research questions:
1) How do carbon and nitrogen uptake rates vary during the summer growing season along the WAP?
2) What is the relative importance of new and regenerated production in the WAP region during summer?
3) How tightly coupled are carbon and nitrogen uptake and cycling in the WAP region during summer?
4) How does carbon and nitrogen recycling vary between different phytoplankton communities?
5) How will ongoing changes in phytoplankton communities impact on regional carbon and nutrient uptake and cycling?

Methodology: This PhD project will involve austral summer fieldwork at the WAP and participation in the large international research effort underway in this region, offering significant opportunities for national and international collaboration. Isotopic enrichment experiments using 15N-labelled nitrate, ammonium, urea and dissolved free amino acids and 14C primary production measurements form the backbone of this PhD. The student will perform these experiments in a laboratory in Antarctica, as well as collecting samples for analysis of upper ocean macronutrient (NO3-+NO2-, PO43-, Si(OH)4) concentrations and phytoplankton species composition. The student will perform the remaining laboratory analyses in the UK and interpret all available data to address the research questions listed above. The student will work within the context of a large interdisciplinary team with many national and international collaborators to fulfil the objectives of this PhD project and maximise the scientific outputs. Ancillary physical, biological and biogeochemical oceanographic data will be available through collaborations.
Year 1: Training in research skills, laboratory techniques and sea-going oceanographic research, familiarisation with relevant scientific literature and refinement of research objectives, fieldwork preparation and implementation.
Year 2: Laboratory analysis, training courses as required, meetings and conferences as appropriate. Obtain relevant additional datasets to provide context for analytical data.
Year 3: Finalise laboratory analyses and compile datasets. Interpret analytical data alongside ancillary datasets to address research questions. Aim to write one peer-reviewed journal article, and begin thesis write-up. Attend meetings and conferences as appropriate.

Training: A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. Advanced training in marine biogeochemical methods will be arranged as required, including fieldwork and laboratory techniques and the relevant health and safety considerations. In addition to the training programme provided by the E4 DTP, there will be opportunities to attend external training courses as agreed by the student and supervisory team.

Requirements: The successful applicant will have at least a 2.1 degree in a relevant scientific discipline. All training will be provided, but experience of scientific fieldwork and/or laboratory techniques would be an advantage. Whilst this project does not require strong pre-existing quantitative skills, a working knowledge of MS Excel as well as programming languages such as R would be beneficial.