International audienceFluorescent dissolved organic matter (FDOM) in coastal marine waters influenced by the municipal sewage effluent (SE) from Marseilles City (France, north-western Mediterranean Sea) has been characterised. Samples were collected eleven times from September 2008 to June 2010 in the Bay of Marseilles along a coast-open sea transect from the SE outlet in the South Bay and at the Mediterranean Institute Observation site in the central Bay. Fluorescence excitation-emission matrices combined with parallel factor analysis (PARAFAC) allowed the identification of two protein-like (tyrosine C1, with excitation maxima (lEx) and an emission maximum (lEm) of ,230, 275/306 nm; tryptophan C2, lEx/lEm,230, 270/346 nm) and three humic-like components (marine humic C3, lEx/lEm 280/386 nm; C4, lEx/lEm 235, 340/410 nm; C5, lEx/lEm 255, 365/474 nm). From the SE outlet to the central Bay, a gradient appeared, with decreasingFDOM intensities, decreasing dissolved organic carbon, particulate carbon, nutrients and faecal bacteria concentrations and increasing salinity values. This gradient was associated with decreasing abundances in protein-like fluorophores and rising abundances in humic-like (C3 and C5) materials. This shift in FDOM composition illustrated the decrease in wastewater inputs and the increase in marine sources of DOM along the transect. FDOM data showed that the Marseilles SE spread up to 1500m off the outlet, but it did not reach the central Bay. Tryptophan-like material was the dominant fluorophore in the SE and displayed the highest correlations with biogeochemical parameters (organic carbon, phosphates, faecal bacteria). Therefore, it is proposed to use its fluorescence intensity to detect and track SE inputs in the Marseilles coastal marine waters

Background Wastewater treatment plants are an essential part of maintaining the health and safety of the general public. However, they are also an anthropogenic source of antibiotic resistance genes. In this study, we characterized the resistome, the distribution of classes 1–3 integron-integrase genes (intI1, intI2, and intI3) as mobile genetic element biomarkers, and the bacterial and phage community compositions in the North End Sewage Treatment Plant in Winnipeg, Manitoba. Samples were collected from raw sewage, returned activated sludge, final effluent, and dewatered sludge. A total of 28 bacterial and viral metagenomes were sequenced over two seasons, fall and winter. Integron-integrase genes, the 16S rRNA gene, and the coliform beta-glucuronidase gene were also quantified during this time period. Results Bacterial classes observed above 1% relative abundance in all treatments were Actinobacteria (39.24% ± 0.25%), Beta-proteobacteria (23.99% ± 0.16%), Gamma-proteobacteria (11.06% ± 0.09%), and Alpha-proteobacteria (9.18 ± 0.04%). Families within the Caudovirales order: Siphoviridae (48.69% ± 0.10%), Podoviridae (23.99% ± 0.07%), and Myoviridae (19.94% ± 0.09%) were the dominant phage observed throughout the NESTP. The most abundant bacterial genera (in terms of average percent relative abundance) in influent, returned activated sludge, final effluent, and sludge, respectively, includes Mycobacterium (37.4%, 18.3%, 46.1%, and 7.7%), Acidovorax (8.9%, 10.8%, 5.4%, and 1.3%), and Polaromonas (2.5%, 3.3%, 1.4%, and 0.4%). The most abundant class of antibiotic resistance in bacterial samples was tetracycline resistance (17.86% ± 0.03%) followed by peptide antibiotics (14.24% ± 0.03%), and macrolides (10.63% ± 0.02%). Similarly, the phage samples contained a higher prevalence of macrolide (30.12% ± 0.30%), peptide antibiotic (10.78% ± 0.13%), and tetracycline (8.69% ± 0.11%) resistance. In addition, intI1 was the most abundant integron-integrase gene throughout treatment (1.14 × 104 gene copies/mL) followed by intI3 (4.97 × 103 gene copies/mL) while intI2 abundance remained low (6.4 × 101 gene copies/mL). Conclusions Wastewater treatment successfully reduced the abundance of bacteria, DNA phage and antibiotic resistance genes although many antibiotic resistance genes remained in effluent and biosolids. The presence of integron-integrase genes throughout treatment and in effluent suggests that antibiotic resistance genes could be actively disseminating resistance between both environmental and pathogenic bacteria.