The CSIR's Dr Thato Mtshali is the first South African research scientist to join the international GEOTRACES-team on its research cruise in the western Pacific Ocean in June.
Established in 2004 by the Scientific Committee on Ocean Research (SCOR), GEOTRACES is a global experiment to help the science community understand past, present and future cycles of trace metals, and how changes in the environment are impacting on these cycles.
Dr Mtshali, an alumni from the University of the Free State, specialises in the biogeochemistry of iron in controlling productivity and carbon fluxes in the Southern Ocean. Currently, he is setting up an experimental facility at Stellenbosch University with funding from the CSIR and the Department of Science and Technology.
Over the past 30 years researchers have made great strides in developing our ability to sample and model trace elements like iron with methods like fluid injection analysis (FIA) and so-called clean labs. As iron has to be sampled in such minute quantities, and as sampling is often taking place off a ship made from all types of steel, sampling methods have become highly sophisticated.
This is also the main reason why Mtshali participated in this cruise, as South Africa is now building the capability to sample and measure a trace metal like iron - one of the essential micronutrients to phytoplankton and a key role player in our understanding of the role of the oceans in global CO2 trends (see the background information at the end of the article). Mtshali worked with the best in the world and aims to employ these methods later on SA's own sampling trips, as well as in the newly-established iron chemistry facility at the University of Stellenbosch - another first for South Africa to come into operation later this year - thereby exponentially increasing South Africa's ability to contribute to the international science community's understanding of the carbon-climate cycle.
Before going on board, Mtshali first had to attend lectures and undergo training in the use of the equipment and sampling methods. GEOTRACES sets the recommended methods for sampling and analysing seawater, following internationally agreed-upon intercalibration standards so that results from different cruises, and from labs from different countries, can be compared in a meaningful way.
According to Dr Pedro Monteiro, leader of the Southern Ocean Carbon-Climate Observatory (SOCCO) programme at the CSIR, sampling data on the availability and characteristics of iron in the Southern Ocean has so far been limited to 'snapshots' obtained by foreign research teams with the appropriate equipment and skills.
"More systematic long-term sampling, at a higher resolution and in combination with numerical models, will enable researchers to better understand the long term trends of the natural carbon-cycle and its vulnerability to human-induced changes to the natural system," Monteiro explains.
The GEOTRACES cruise is but one element in a national programme funded by the Department of Science and Technology to enhance South Africa's capacity to contribute to the global science community's understanding of the role of the Southern Ocean in the global carbon-climate cycle.
Some metals, such as iron, are essential micronutrients to phytoplankton. However, in many regions of the world's oceans the concentrations of these metals are so low they limit biological growth. Photosynthesis is the single most important natural process whereby carbon is taken up by phytoplankton in the oceans in the natural carbon cycle. As a result of phytoplankton photosynthesis, some of the CO2 derived from fossil fuels is 'exported' into the deep ocean as particulate organic carbon when phytoplankton cells die and sink. As the organic carbon slowly sinks, taking as long as two to three months to get from the surface to the sea floor at about three to five kilometres, bacteria decompose this organic carbon into dissolved inorganic carbon. This will stay in the deep oceans for hundreds to thousands of years. This effectively removes CO2 and its warming influence from the atmosphere.
However, this cannot happen without iron and the Southern Ocean is iron poor. The dust blowing from land masses are the main source of iron to the world's oceans, but as the Southern Hemisphere is dominated by oceans and not land, it is a typical 'high-nutrient-low-chlorophyll' ocean.
Pedro Monteiro, Mike Lucas and Guy Midgley, Iron in the oceans, Cape Argus, 15 January 2009).
Mike Lucas, Pumping iron and climate control in Quest 6(3)2010:36-38)