A new international study, coordinated by Francesca Malfatti, Professor of Microbiology at the Department of Life Sciences of the University of Trieste, has revealed how black carbon can significantly influence microbial communities in the marine environment, with important implications for the global carbon cycle and the functioning of ocean ecosystems. The research, published in the journal Environmental Science and Pollution Research, involved a team of researchers from the Oceanography Department of the National Institute of Oceanography and Applied Geophysics (OGS), Elettra and several French and Austrian research institutions.

Black carbon, the focus of the study, is a residue resulting from the incomplete combustion of fossil fuels, wood, biomass or biofuels. It makes up a significant fraction of atmospheric particulate matter and can reach the ocean through rain, wind or river runoff. Due to its ability to absorb heat, it also contributes to global warming.

Through experiments carried out in the Ligurian and Adriatic Seas, the researchers simulated high concentrations of black carbon (24 mg per litre) to observe how marine microbial communities reacted to its presence. The results showed that black carbon can stimulate the growth of heterotrophic prokaryotic microorganisms, which feed on organic matter in the water, and increase the production of organic carbon, making it available to other marine organisms.

However, the same experiments showed a decrease in enzymatic activity, which normally promotes the degradation of organic matter, and a reduced presence of viruses. This suggests that black carbon alters the microbial balance, creating environmental micro-niches in which microorganisms with specific metabolic functions proliferate.

These results help to better understand the functioning of the so-called ‘microbial carbon pump’ (MCP), a mechanism that transforms organic matter into more stable forms, capable of remaining in the ocean for long periods and thus contributing to carbon storage. Studying the role of black carbon, especially that of anthropogenic origin, is therefore essential for improving climate change models and developing effective mitigation strategies.