Black carbon’s colonisation by microbes

Black carbon is a pyrogenic material produced during the incomplete combustion of fossil fuels, bio-fuels and biomass. Its effects on the marine environment are understudied, particularly those on biogeochemical cycling. Black carbon particles are known to be reactive, due to their porous structure and external coverage of oxygen-containing functional groups. Other molecules react with these groups, (such as amino acids) resulting in adherence and aggregation. This study examines the way amino acid-amended black carbon is colonised by microbes. The researchers took SML samples, and added seawater and commercial black carbon. They then divided this sample into 15 bottles. 9 of these samples were amended with a 15N labelled algal amino acid mix, before being incubated for 12, 24 and 48 hours. 6 samples were used as controls, with 3 of them incubated for 48 hours and 3 used as “zero-hour” samples. The controls were not amended with the amino acid mix. The incubation was followed with nanoSIMS analysis. The results showed an increase in amino acid adsorption over time, leading to an increase in bacterial abundance in the experimental treatments. The researchers conclude that black carbon adsorption of amino acid molecules results in an increase in colonising bacteria on the particles. They discuss how this may be useful in remineralising the carbon, but also discuss how the “diversion” of the bacteria could disrupt the biological carbon pump, and how it is unclear whether remineralisation is actually occurring.

Benavides M, Chu Van T, Mari X, (2019), Amino acids promote black carbon aggregation and microbial colonisation in costal water off Vietnam, Science of the total environment, pp. 527-532