Nitrogen Transformations in Stream Sediments:

Comparison of DET, DGT and conventional porewater extractions for determining nutrient profiles and cycling in stream sediments

Environmental Science Processes & Impacts ◽

10.1039/c9em00312f ◽

2019 ◽

Vol 21 (12) ◽

pp. 2128-2140 ◽

Cited By ~ 3

Author(s):

Jianyin Huang ◽

Hannah Franklin ◽

Peter R. Teasdale ◽

Michele A. Burford ◽

Nadeeka Rathnayake Kankanamge ◽

...

Keyword(s):

Aquatic Plants ◽

Benthic Microalgae ◽

Stream Sediments ◽

Passive Samplers ◽

Nitrogen Transformations ◽

Nutrient Profiles ◽

Sediment Heterogeneity ◽

Measurement Capabilities

Passive samplers measurements, especially DET, contributed to understanding of nitrogen transformations and sediment heterogeneity influenced by benthic microalgae, rooted aquatic plants and/or diel light cycles. Measurement capabilities varied considerably, especially for NH4–N.

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Are nitrogen and carbon cycle processes impacted by common stream antibiotics? A comparative assessment of single vs. mixture exposures

PLoS ONE ◽

10.1371/journal.pone.0261714 ◽

2022 ◽

Vol 17 (1) ◽

pp. e0261714

Author(s):

Austin D. Gray ◽

Emily Bernhardt

Keyword(s):

Microbial Communities ◽

Nitrogen Cycling ◽

Carbon Fixation ◽

Inorganic Nitrogen ◽

Combined Treatment ◽

Stream Sediments ◽

Freshwater Ecosystems ◽

Nitrogen Transformations ◽

Community Resistance ◽

Mixture Treatment

A variety of antibiotics are ubiquitous in all freshwater ecosystems that receive wastewater. A wide variety of antibiotics have been developed to kill problematic bacteria and fungi through targeted application, and their use has contributed significantly to public health and livestock management. Unfortunately, a substantial fraction of the antibiotics applied to humans, pets and livestock end up in wastewater, and ultimately many of these chemicals enter freshwater ecosystems. The effect of adding chemicals that are intentionally designed to kill microbes, on freshwater microbial communities remains poorly understood. There are reasons to be concerned, as microbes play an essential role in nutrient uptake, carbon fixation and denitrification in freshwater ecosystems. Chemicals that reduce or alter freshwater microbial communities might reduce their capacity to degrade the excess nutrients and organic matter that characterize wastewater. We performed a laboratory experiment in which we exposed microbial community from unexposed stream sediments to three commonly detected antibiotics found in urban wastewater and urban streams (sulfamethoxazole, danofloxacin, and erythromycin). We assessed how the form and concentration of inorganic nitrogen, microbial carbon, and nitrogen cycling processes changed in response to environmentally relevant doses (10 μg/L) of each of these antibiotics individually and in combination. We expected to find that all antibiotics suppressed rates of microbial mineralization and nitrogen transformations and we anticipated that this suppression of microbial activity would be greatest in the combined treatment. Contrary to our expectations we measured few significant changes in microbially mediated functions in response to our experimental antibiotic dosing. We found no difference in functional gene abundance of key nitrogen cycling genes nosZ, mcrA, nirK, and amoA genes, and we measured no treatment effects on NO3- uptake or N2O, N2, CH4, CO2 production over the course of our seven-day experiment. In the mixture treatment, we measured significant increases in NH4+ concentrations over the first 24 hours of the experiment, which were indistinguishable from controls within six hours. Our results suggest remarkable community resistance to pressure antibiotic exposure poses on naïve stream sediments.

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