Black carbon structuring marine microbial activities and interactions: a micro- to macro-scale interrogation

Black carbon (BC) consists of partially combusted organic matter deriving from biomass and fuels burning. According to the IPCC’s reports, BC emissions are the second-largest contributor to global warming after CO2. BC enters the marine system via dry deposition or river run-off. Once in the sea, BC has the potential to affect nutrient biogeochemical cycles. In a series of four incubation experiments (Adriatic Sea and Ligurian Sea) and a pilot study, we have challenged the microbes with heavy loads of BC (24 mg L−1) in order to study the short-term BC effect on microbial dynamics and activities. Upon BC amendment, heterotrophic prokaryotes increased in abundance while viruses decreased. At the microscale, microbes became attached to BC particles, very heterogeneous in shape and size and enriched in proteins over time; these findings were confirmed by Fourier transform-IR spectroscopy and atomic force microscopy. Enzymatic degradative activities, proteases, and alkaline phosphatases wer...