Potential impacts of black carbon on the marine microbial community

Abstract

Black carbon (BC) is the carbonaceous residue of the incomplete combustion of fossil fuels and biomass and encompasses a range of chemically heterogeneous substances from partly charred plant material to highly condensed soot aerosols. We addressed the potential role of BC aerosol deposition on marine microbial processes in the ocean by investigating the effects of BC reference material (and its exposure to simulated solar radiation) on viral and bacterial activity in batch cultures with aged seawater. Viruses and bacteria were rapidly adsorbed to BC. No difference between the effect of irradiated and non-irradiated BC on free viral parameters was observed. Bacterial leucine incorporation was higher in the BC treatments than in the BC-free controls. The stimulated bacterial production in the dark BC treatments might be caused by the reduction of viral infection due to adsorption of organic material or by direct use of BC material. Viral production was significantly lower in BC-amended treatments than in BC-free controls, and the estimated fraction of infected cells decreased with increasing BC concentration. Moreover, bacterial activity in the solar-radiation-exposed BC treatments was higher than in the dark BC treatments, indicating that radiation made BC more accessible to bacteria. Our data reveal that BC has the potential to stimulate bacterial activity in the water column, particularly after exposure to solar radiation. Rising BC levels in the atmosphere due to increasing anthropogenic emissions could have far-reaching effects, including potential stimulation of seawater heterotrophy and CO 2 production, through its effects on bacteria and viruses.

Bacterial-viral interactions in the sea surface microlayer of a black carbon-dominated tropical coastal ecosystem (Halong Bay, Vietnam)

“…Higher BP rates (by 5-fold), however, were also observed in the SML in our study, along with significant positive correlations between BP and other environmental parameters, including particulate and dissolved BC concentrations ( Table 2). The highest BP was measured at the station which coincided with the highest concentrations of both BC and ammonium, suggesting that bacterial activity might have been stimulated by the combined action of both variables, as demonstrated in laboratory experiments (Malits et al, 2015). We thus suggest that our observations support conclusions of recent studies, specifically that BC can be an important source of carbon for bacterial utilization as it can be made available to the bacterial community through photochemical (Stubbins et al, 2012) and microbial oxidation (Zimmerman, 2010), thereby challenging the previous assumption of its refractory and chemically recalcitrant nature.…”

“…Ultimately, by impacting the physiological state of bacteria and their overall community metabolism, the bacterial utilization of black carbon becomes a potential factor influencing viral life strategies in aquatic systems (Maurice et al, 2013;Palesse et al, 2014). Previous reports have suggested that virally mediated bacterial mortality decreases with an increase in BC concentration (Mari et al, 2014;Malits et al, 2015). Bacterial cells may be trapped within BC particles, which could result in the hiding of bacterial receptors thereby lowering the chances of viral infection.…”

“…Previous reports have shown that bacteria and viruses were efficiently adsorbed onto BC particles (Mari et al, 2014;Malits et al, 2015). Such phenomenon can be expected to impact bacterial production (BP) and viral lysis, and hence biogeochemical cycles.…”

Flow Cytometric Determination of Microbial Abundances and Its Use to Obtain Indices of Community Structure and Relative Activity

“…Recent studies have evidenced that bacteria attach to inorganic particles, either (standard) black carbon particles [45] or naturally produced deep-sea volcano ventilation material [46]. In these cases (example in Fig.…”

“…8 Example of a prokaryotic sample observed with blue light excitation after staining with SYBR Green I, where particle-attached bacteria can be enumerated. The sample corresponds to North Sea water [45]. The beads (B) are Invitrogen 1 μm.…”