UP team sheds light on biological activity in the twilight zones

Posted on September 19, 2019

Five UP researchers from the Centre for Microbial Ecology and Genomics (CMEG) in the Department of Biochemistry, Genetics and Microbiology recently returned from a successful expedition to the Southern Ocean. Postgraduate students Percy Lunga, Mancha Mabas and Diego Castillo, and postdoctoral fellows Drs Jessica Koopman and Jarishma Gokul participated in the Southern oCean seAsonaL Experiment (SCALE) cruise. The UP team was part of a group of 100 international scientists from more than 18 countries who spent three weeks on board the South African ice-breaker vessel RV SA Agulhas II. The primary objective of the cruise was to gain an understanding of seasonal variability in this important ocean.

While most people know that oceans are important for transporting goods and services, their vital roles in transporting nutrients and heat, and in the sequestration of carbon dioxide are less well known. These lesser-known roles are important for regulating the Earth’s climate. Although the Southern Ocean covers only 20% of the global ocean area, recent estimates suggest that more than 40% of all anthropogenic carbon dioxide is stored there.

The group undertook a series of activities aimed at clarifying the role of microbial communities and their impact on climate change. Although the role played by other marine organisms has been thoroughly researched, very little is known regarding the diversity and functional roles of these organisms that have a direct impact on global warming, particularly in the twilight zones of the ocean. Led by Dr Thulani Makhalanyane, the young researchers from UP used metagenomics and bioinformatics tools to determine the identity and potential functions of archaea, bacteria and viruses that inhabit the depths of the Southern Ocean.

During the voyage, they obtained samples from nine sites along the sampling transect. At each site, water samples were collected from eight depths, which included bottom samples taken at a depth of more than four kilometers. A rosette holding 24 bottles with a capacity of 20 litres each was deployed at each station. Water from these bottles was then used for more than eight different experiments, which included the filtering of water to trap microorganisms, radioisotope experiments to determine carbon uptake, and nutrients analysis.

The results obtained from this interdisciplinary project will be compared to those obtained during the second leg of the project, which will be undertaken next spring. The UP team had a very important role in SCALE as they were the only scientists on board who focused on the involvement of microorganisms in the seasonal cycle model.

In addition to providing samples for several master’s and PhD programmes, the knowledge generated from this expedition will contribute directly to shedding light on the roles played by microbial communities in the Southern Ocean and their impact on climate change.

- Author CMEG

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