Improving conditions for nutrient-transforming microbial communities in multi-zoned biofilters to help prevent eutrophication of downstream reservoirs

Sequential sedimentation-biofiltration systems (SSBSs) are nature-based solutions that aid in the removal of pollutants carried by urban stormwater runoff. They are multi-zoned biofilters constructed within the structure of urban rivers, providing water treatment, and preventing anthropogenic eutrophication with the appearance of CyanoHABs in downstream waterbodies. Microbial communities play an important role in the cycling of nutrients in natural environments. Therefore, we investigated the dynamics of microbial metabolic activity, the abundance of nitrifying (gene amoA), and denitrifying bacteria (nosZ) in SSBSs. Furthermore, bacterial populations were characterized in zones containing biofilm (16S rRNA), and bacteria were isolated from sediments and tested for their metabolic properties. Results indicated that microbial metabolic activity was higher in summer. The geochemical zone -containing limestone- showed the highest abundance of nitrifiers in spring. The denitrifying zone -with brown coal- presented the highest abundance of denitrifiers in summer. Two isolated strains -Citrobacter freundii Bzr02 and Pseudomonas mandelii Str21- showed biotechnological potential in removal of nitrogen compounds during laboratory assays. These results suggested future modifications in the construction of SSBSs that could enhance the abundance and activity of microbial communities, to improve their efficiency in nutrient removal and mitigate CyanoHABs. Funds: National Centre for Research and Development TANGO2/339929/NCBR/2017 “AZOSTOP

Temporal variation in microcystin production by

Eutrophication of freshwater lakes has led to blooms formed by cyanobacteria often associated with toxins harmful to livestock and humans. Environmental conditions that favor toxin production during cyanobacterial blooms are, however, not well understood. Moreover, the ability to use cyanobacteria quantity to assess the level of threat associated with toxin production is a topic of discussion. The purpose for this study was to examine Planktothrix agardhii dynamics in a shallow, temperate hypertrophic lake and to determine the factors that affect microcystin production. In addition, the relationship between P. agardhii morphology and microcystin production was examined. The study spanned 2 years, and we documented a perennial P. agardhii bloom that contributed up to 99% of the total biomass. Intracellular microcystins were primarily detected throughout the study, with the highest concentration in October. Microcystin concentrations ranged from 3.4 to 71.2 μg.L−1, and they had a strong, positive correlation with P. agardhii biomass. In contrast, the levels of weight-specific microcystin were relatively stable throughout the entire study, ranging from 0.23 to 1.18 μg.mg−1. We also found that environmental factors, such as water temperature, phosphate level, ammonium nitrogen and transparency, were the most related to microcystin production. Furthermore, a significant relationship between filament morphology and toxin concentration suggested that there were different morphotypes within the toxic and non-toxic populations of P. agardhii. Our study showed that P. agardhii biomass and filament morphology may be useful characteristics for the identification of threats associated with cyanotoxins

Pearson correlation coefficients between precipitation and flow (measured 5 days prior to sample collection) and ELISA-EQ concentration of PCDDs/PCDFs and triclosan in all the samples, stormwater samples, reservoir samples and river samples.

<p>Pearson correlation coefficients between precipitation and flow (measured 5 days prior to sample collection) and ELISA-EQ concentration of PCDDs/PCDFs and triclosan in all the samples, stormwater samples, reservoir samples and river samples.</p

Average ELISA-EQ concentrations of PCDDs/PCDFs and triclosan during the 5 sampling periods.

<p>Average ELISA-EQ concentrations of PCDDs/PCDFs and triclosan during the 5 sampling periods.</p