​​​​​​​Johan ViljoenProfile Photo.jpg

PhD Candidate – Marine Biogeochemistry , Earth Sciences Department, Stellenbosch University
Earth Science Postgraduate Representative

Contact and Social Media Details:

Twitter: @JohanSOV



Research and current projects:

I’m a marine biogeochemist specialising in Southern Ocean phytoplankton dynamics, which includes identifying and quantifying phytoplankton groups using their pigment signatures, assessing the photoprotective states and adaptability of phytoplankton within varying light environments and varying conditions of iron-light co-limitation within different water masses. The focus of my MSc was to determine the distribution and adaption of phytoplankton and their links to various essential trace metals within the Atlantic Southern Ocean using observational HPLC-determined latitudinal pigment concentrations and an experimental study assessing the co-limitation of light and iron on the phytoplankton productivity and community composition. I make use of the matrix factorisation software CHEMTAX to assist in estimating the phytoplankton community compositions from HPLC pigment concentration data.
To date I have participated in two research cruises on board South Africa’s flagship research vessel, the SA Agulhas II. During one of these research cruises, a summer resupply cruise to Antarctica (SANAE 56: Nov 16 – Feb 17), I   collected samples for multiple projects. I also wrote a blog about my experience on the Antarctic ice shelf found here. During this cruise, I experienced the rough Southern Ocean and quickly found my sea legs.  I participated in the second cruise as a member of our TracEx team. This was  a winter research cruise to the Antarctic ice edge (July 2017) within the Indian sector of the Southern Ocean along the 30°E longitude south east of South Africa. A video summarising what we did and experienced on this cruise can be found here.
My research interest are mainly phytoplankton pigments, iron-light co-limitation, role various essential trace metals have on phytoplankton dynamics and vice versa and the analysis of phytoplankton pigment using High Performance Liquid Chromatography (HPLC). My goal is to setup the analysis of marine pigments via HPLC here within the TracEx labs together with other TracEx team members. 


Current Role and projects:

I’m a postgraduate student researcher within the Centre for Trace and Experimental Biogeochemistry (TracEx) at the Department of Earth Sciences.
Part of TracEx research group with my responsibilities being the identification and abundance estimation via HPLC pigment data for each research of the team. On cruises, I am responsible for the sampling of phytoplankton pigments, macronutrients and particulate organic carbon and assist with preparations for trace metal sampling.
The projects that I’m involved in forms part of a larger project within the South African National Antarctic Programme (SANAP)​ of which the main aim is to understand the biological and biogeochemical processes occurring in the Southern Ocean and how this is linked and will affect our global climate.
I also serve as a national committee member within the South African branch of the Association for Polar Early Career Scientists (APECS) – APECS-SA.


Academic qualifications:

B.Sc Earth Science (2013-2015) - Department of Earth Sciences, Stellenbosch University 
B.Sc (Honours) Earth Science - Environmental Geochemistry (2016), Department of Earth Sciences, Stellenbosch University
M.Sc Earth Science (Cum Laude) - Marine Biogeochemistry (2017-2018), Department of Earth Sciences, Stellenbosch University. 
PhD Earth Science – Marine Biogeochemistry (2019-present), Department of Earth Sciences, Stellenbosch University



Viljoen, J. J.*, R. Philibert*, N. Van Horsten, T. Mtshali, A. N. Roychoudhury, S. Thomalla, and S. Fietz. 2018. Phytoplankton response in growth, photophysiology and community structure to iron and light in the Polar Frontal Zone and Antarctic waters. Deep Sea Res. I. https://www.sciencedirect.com/science/article/pii/S0967063718301420?via%3Dihub

 Viljoen, J.J., Weir, I., Fietz, S., Cloete, R., Loock, J., Philibert, R., Roychoudhury, A.N., 2019. Links between the phytoplankton community composition and trace metal distribution in summer surface waters of the Atlantic Southern Ocean. Front. Mar. Sci. 6, 295. https://doi.org/10.3389/fmars.2019.00295 ​ 

Conference outputs:​

South African National Antarctic Programme (SANAP) Symposium 2018, Hermanus: Southern-Atlantic phytoplankton community composition, distribution and response to relief of light and iron limitation
POLAR/SCAR Open Science Conference 2018, Davos: Southern-Atlantic phytoplankton community composition response to light and iron
UCT & Stellenbosch University Postgraduate Science Symposium - Poster: Southern-Atlantic phytoplankton community composition response to light and iron (poster available on Research Gate)