Effects of Sulfamethazine on Denitrification and the Associated N₂O Release in Estuarine and Coastal Sediments

Abstract

Denitrification is an important pathway of nitrogen removal and nitrous oxide (N2O) production in estuarine and coastal ecosystems, and plays a significant role in counteracting aquatic eutrophication induced by excessive nitrogen loads. Estuarine and coastal environments also suffer from increasing antibiotic contamination because of the growing production and usage of antibiotics. In this study, sediment slurry incubation experiments were conducted to determine the influence of sulfamethazine (SMT, a sulphonamide antibiotic) on denitrification and the associated N2O production. Genes important for denitrification and antibiotic resistance were quantified to investigate the microbial physiological mechanisms underlying SMT's effects on denitrification. SMT was observed to significantly inhibit denitrification rates, but increasing concentrations of SMT enhanced N2O release rates. The negative exponential relationships between denitrifying gene abundances and SMT concentrations showed that SMT reduced denitrification rates by restricting the growth of denitrifying bacteria, although the presence of the antibiotic resistance gene was detected during the incubation period. These results imply that the wide occurrence of residual antibiotics in estuarine and coastal ecosystems may influence eutrophication control, greenhouse effects, and atmospheric ozone depletion by inhibiting denitrification and stimulating the release of N2O.

Antibiotics and the Terrestrial Nitrogen Cycle: A Review

“…Because the increase in N 2 O flux coincided with inhibited denitrification, the authors propose that antibiotics may more strongly inhibit N 2 O reduction to N 2 than N 2 O production itself, resulting in an increased N 2 O:N 2 production ratio [116]. DeVries et al [112] proposed a similar conclusion upon observing a threefold increase in N 2 O flux in soils amended with 1-1000 ng·kg −1 NAR after a 3-day incubation.…”

“…The effects of 18 different antibiotics on denitrification have been investigated, and the results vary considerably among the different solid matrices and concentrations tested ( except where SMZ (0.05-100 μg·L −1 ) was applied [116].…”

“…Resistance is less likely to develop in short-term experiments following a single antibiotic dose, which may explain why Hou et al [116] were able to observe inhibition in sediments 1-8 h after they were treated with lower doses of SDZ (0.05-100 μg·L…”

“…Both observed a rise N 2 O flux in soils treated with sub-therapeutic doses of antibiotics. Hou et al [116] tested the effects of SMZ (0.05-100 μg·L…”

Do antibiotics have environmental side-effects? Impact of synthetic antibiotics on biogeochemical processes

“…Across studies, the fate of the antibiotic substance during the experiment was often unconsidered, and only 40 % of the studies quantified the antibiotic concentration in the experimental medium to determine the effect on a certain process (Ahmad et al 2014;Campos et al 2001;Hansen et al 1992;Hou et al 2015;Kotzerke et al 2008;Kotzerke et al 2011;Liu et al 2014;Rico et al 2014 Effective concentration Effective concentration Rosendahl et al 2012;Thiele-Bruhn and Beck 2005;Yan et al 2013). Regardless the antibiotic family, these studies revealed considerable loss of antibiotics over the experiment.…”