Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Science of the Total Environment 165802 [18 ] [+ Corrigendum, vol. 904, 166251] Black carbon Soot Dissolved organic matter Marine prokaryotes Bioavailability Bacterial degradation MEDITERRANEE FRANCE MARSEILLE 2023 fdi:010090136 ENG Science of the Total Environment 0048-9697 ISI:001052992800001 10.1016/j.scitotenv.2023.165802 https://www.documentation.ird.fr/hor/fdi:010090136 https://www.documentation.ird.fr/intranet/publi/2023-10/010090136.pdf 901 Horizon (IRD) Here we investigated the bioavailability of black carbon (BC)-derived dissolved organic matter (DOM) for a natural mixed community of marine heterotrophic prokaryotes. We ran an in vitro biodegradation experiment that took place over 3 months and exposed a community of organisms collected in the northwestern Mediterranean Sea (Bay of Marseille, France) to three different soluble fractions of BC prepared in the laboratory from various fossil fuel combustion particulates: standard diesel (DREF), oxidized diesel (DREF-OX), and natural samples of ship soot (DSHIP). Over the course of the three months, we observed significant decreases in the concentrations of dissolved organic carbon (DOC; from 9 to 21 %), dissolved BC (DBC; from 22 to 38 %) and dissolved polycyclic aromatic hydrocarbons (d-PAH; from 24 to 64 %) along with variability in the growth dynamics and activity of the heterotrophic prokaryotic community. The heterotrophic prokaryotic community exposed to DREF-OX treatment showed the highest values of respiration and production and the highest cell abundance, associated with the highest decrease in DOC (21 %) and d-PAH (64 %) concentrations. In the DREF and DSHIP treatments, prokaryotic activity was oriented towards anabolism. DREF treatment led to the highest decrease in DBC concentration (38 %). DSHIP treatment, which presented a substantially different d-PAH and dissolved metals content to the other two treatments, showed the lowest decreases in DOC, DBC and d-PAH concentrations, as well as the lowest prokaryotic activity and biomasses. Our results indicate that BC-derived DOM, including the most condensed fraction of this material, is partly bioavailable and therefore likely to be assimilated by marine prokaryotes. The origin of BC/soot deposited at the ocean surface turns out to be a key parameter that dictates the efficiency of biodegradation of its dissolved fraction by heterotrophic prokaryotes. 021 ; 034 ; 084 UR235 Vietnam