Dissolved organic carbon (DOC) dynamics in streams is important, yet few studies focus on DOC dynamics in Midwestern streams during storms. In this study, stream DOC dynamics during storms in two Midwestern watersheds with contrasting land uses, the change in character of stream DOC during storms, and the usability of DOC as a hydrologic tracer in artiWcially drained landscapes of the Midwest are investigated. Major cation/DOC concentrations, and DOC speciWc UV absorbance (SUVA) and Xuorescence index (FI) were monitored at 2-4 h intervals during three spring storms. Although DOC is less aromatic in the mixed land use watershed than in the agricultural watershed, land use has little impact on stream DOC concentration during storms. For both watersheds, DOC concentration follows discharge, and SUVA and FI values indicate an increase in stream DOC aromaticity and lignin content during storms. The comparison of DOC/major cation Xushing dynamics indicates that DOC is mainly exported via overland Xow/macropore Xow. In both watersheds, the increase in DOC concentration in the streams during storms corresponds to a shift in the source of DOC from DOC originating from mineral soil layers of the soil proWle at baseXow, to DOC originating from surWcial soil layers richer in aromatic substances and lignin during storms. Results also suggest that DOC, SUVA and FI could be used as hydrologic tracers in artiWcially drained landscapes of the Midwest. These results underscore the importance of sampling streams for DOC during high Xow periods in order to understand the fate of DOC in streams.

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Background Wastewater surveillance was proposed as an epidemiological tool to define the prevalence and evolution of the SARS-CoV-2 epidemics. However, most implemented SARS-CoV-2 wastewater surveillance projects were based on qPCR measurement of virus titers and did not address the mutational spectrum of SARS-CoV-2 circulating in the population. Methods We have implemented a nanopore RNA sequencing monitoring system in the city of Nice (France, 550,000 inhabitants). Between October 2020 and March 2021, we monthly analyzed the SARS-CoV-2 variants in 113 wastewater samples collected in the main wastewater treatment plant and 20 neighborhoods. Findings We initially detected the lineages predominant in Europe at the end of 2020 (B.1.160, B.1.177, B.1.367, B.1.474, and B.1.221). In January, a localized emergence of a variant (Spike:A522S) of the B.1.1.7 lineage occurred in one neighborhood. It rapidly spread and became dominant all over the city. Other variants of concern (B.1.351, P.1) were also detected in some neighborhoods, but at low frequency. Comparison with individual clinical samples collected during the same week showed that wastewater sequencing correctly identified the same lineages as those found in COVID-19 patients. Interpretation Wastewater sequencing allowed to document the diversity of SARS-CoV-2 sequences within the different neighborhoods of the city of Nice. Our results illustrate how sequencing of sewage samples can be used to track pathogen sequence diversity in the current pandemics and in future infectious disease outbreaks. Translation For the French translation of the abstract see Supplementary Materials section.

This research estimates phytoplankton pigment concentrations (chlorophyll-a (chl-a) and phycocyanin (PC)) from hyperspectral Airborne Imaging Spectrometer for Applications (AISA) imagery. AISA images were acquired for a meso-eutrophic reservoir in Central Indiana, USA. Concurrent with the airborne image acquisition, in situ water samples and reflectances were collected. The water samples were subsequently analysed for pigment concentrations, and in situ measured reflectance spectra were used for calibrating the AISA images. Spectral indices, derived from the AISA reflectance spectra, were regressed against the measured pigment concentrations to derive algorithms for estimating chl-a and PC. The relationship between the pigment concentrations and the spectral indices were analysed and evaluated. The results indicate that the highest correlation occurred between chl-a and a nearinfrared to red ratio (coefficient of determination R 2 ¼ 0.78) and between PC and the reflectance trough at 628 nm (R 2 ¼ 0.80). The relationship between PC and the reflectance at 628 nm provides an approach to the estimation of cyanobacteria concentration from hyperspectral imagery, which facilitates water-quality authorities or management agencies in making well-informed management decisions.

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