My Ph.D. research is part of broader research by the Swiss Polar Institute’s Antarctic Circumnavigation Expedition (ACE). ACE is made up of 22 different projects bringing together research teams from six continents. The projects focus on different areas of study with the aim to understand and answer questions about the Antarctic ecosystem. My work is a segment in South Africa’s ACE XII which seeks to understand how microbial community composition affects organic carbon export in the Southern Ocean, and how this changes with changing nitrogen source. Using a combination of cutting-edge chemical, biological, and computation techniques, we aim to answer the following questions regarding the microbial community in the open Southern Ocean: Who is there? What are they doing? Why are they doing it? What are the implications for Antarctic nitrogen cycling, ecosystem function, and atmospheric COabsorption, today and in a warming world? This work has implications for South Africa’s Oceans economy, as Antarctic waters currently support globally-significant fisheries, as well as for the management of vulnerable ecosystems.

ACE XII, Principal Investigator, Dr Sarah Fawcett

The Ph.D. project focuses on the application of a combination of molecular and chemical techniques to explore the structure and activities of microbial communities. The project additionally evaluates community changes in relation to nutrient concentration fluctuations, sources and ratios. Microbe-nutrient interactions concentrate on nitrogen (N) due to the nutrient’s existence in marine systems in copious forms. In driving carbon export, roles of different species of phytoplankton, sources and different forms of N found in the upper ocean waters and N supplied to island systems are analysed with the objectives to quantify new production.

Samples to be analysed were obtained from the vicinity of the Prince Edward volcanic islands, upstream, downstream and in between the two islands (Figures 1& 2). For nutrients and N isotopes, samples were collected from 11 stations, from 6 stations for FACS, 11 stations for flow cytometry and 10 stations for DNA/RNA.  On the way back from the Subantarctic islands to Cape Town, more sampling took place along the Crossroads line (Figures 1& 3). On the Crossroads line, nutrients and nitrogen isotopes samples were collected from 16 CTD casts, 10 CTD casts for flow cytometry. From the underway system, 5 FACS stations and 4 DNA/ RNA stations were sampled from.

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Figure 1: Representation of Prince Edward Islands and the Crossroads Line (bold red line) on a Google Earth map
Figure 2: Subantarctic marine systems sampling sites- downstream, upstream and inter-island
Figure 3: Crossroads Line sampling sites

The FACS analysis for collected samples takes place at the Institute of Infectious Disease and Molecular Medicine (IDM) at the University of Cape Town’s Medical School with Ronnie Dreyer.

IDM, UCT Medical School
Cell sorting using side/ forward scatter and custom fluorochromes for Synechococcus (cyanobacterial cells) and eukaryotic cells

DNA analyses for 16S rRNA and 18S rRNA took place at Rhodes University’s Department of Biochemistry and Microbiology in Professor Rosemary Dorrington‘s Marine Natural Products laboratory.

The Molecular Science laboratory at Rhodes University
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DNA extraction and Polymerase Chain Reaction (PCR) of collected samples

Macronutrient analyses for nitrate (NO3), nitrite (NO2), phosphate and silicate are taking place at the Marine Biogeochemistry Laboratory in the Oceanography Department at the University of Cape Town under the supervision of Dr Sarah Fawcett.

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Marine Biogeochemistry, UCT. Macro nutrient analyses of collected samples

Lab work is basically processing samples into data that can be analysed to better understand our natural marine systems and to answer the unknowns. I’m excited about the outcomes of all the SCIENCE!

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