Department Surface Waters - Research and Management

Lake productivity is fundamental to biogeochemical budgets as well as estimating ecological state and predicting future development. Combining modelling with Earth Observation data facilitates a new perspective for studying lake primary production. In this study, primary production was modelled in the large Lake Geneva using the MEdium Resolution Imaging Spectrometer (MERIS) image archive for 2002–2012. We used a semi-empirical model that estimates primary production as a function of photosynthetically absorbed radiation and quantum yield of carbon fixation. The necessary input parameters of the model—concentration of chlorophyll a, downwelling irradiance, and the diffuse attenuation coefficient—were obtained from MERIS products. The primary production maps allow us to study decennial temporal (with daily frequency) and spatial changes in this lake that a single sample point cannot provide. Modelled estimates agreed with in situ results (R² = 0.68) and showed a decreasing trend (∼27%) in production in Lake Geneva for the selected decade. Yet, in situ monitoring measurements missed the general increase of productivity near the incoming Rhône River. We show that the temporal and spatial resolution provided by satellite observations allows estimates of primary production at the basin-scale. The phytoplankton annual primary production was estimated as ∼302 (SD 20) g C m⁻² yr⁻¹ for Lake Geneva for 2003 to 2011. This study demonstrates that maps of primary production can be obtained even with reduced resolution (1200  m) MERIS data and relatively simple methods, and thereby calls for deeper integration of remote sensing products into conventional in situ observation approaches.

To compare the performance and antibiotic-resistance character in different process configurations under different levels of antibiotics, anoxic/oxic-membrane bioreactors (MBR) 1#, MBR2# and a sequencing batch reactor (SBR) were operated with identical operating parameters. MBR1# and SBR were operated under high and increasing levels of antibiotics, MBR2# received constant and low concentration of antibiotics. Microbiological community and antibiotic resistance genes (ARGs) were investigated using 16S rDNA gene high-throughput sequencing and qPCR. More than 90% of penicillin and chlortetracycline were removed due to strong hydrolysis, followed by sulfamethoxazole (69.27%–86.25%) through biodegradation and norfloxacin (28.66%–53.86%) through adsorption. Process configuration affected total nitrogen removal more, while antibiotics concentration affected total phosphorus removal more. MBR1# outperformed SBR in reducing sulfamethoxazole, norfloxacin and ARGs due to the retention effect of the membrane module. Retention efficiency of ARGs in MBRs increased along the operation. Compared to the operational taxonomic unit (OTU) number before antibiotics addition, the OTU number in MBR1# and SBR decreased by 23.7% and 28.7%, while that in MBR2# kept relatively stable. Process configuration contributed to higher dissimilarity of microbial community than antibiotics concentration. The research provides an insight into the influence factors of antibiotics-containing wastewater treatment.