title: Nanosilver inhibits nitrification and reduces ammonia-oxidising bacterial but not archaeal amoA gene abundance in estuarine sediments.
abstract: Silver nanoparticles (AgNPs) enter estuaries via wastewater treatment effluents, where they can inhibit microorganisms, because of their antimicrobial properties. Ammonia-oxidising bacteria (AOB) and archaea (AOA) are involved in the first step of nitrification and are important to ecosystem function, especially where effluent discharge results in high nitrogen inputs. Here, we investigated the effect of a pulse addition of AgNPs on AOB and AOA ammonia monooxygenase (amoA) gene abundances and benthic nitrification potential rates (NPR) in low-salinity and mesohaline estuarine sediments. Whilst exposure to 0.5 mg L-1AgNPs had no significant effect on amoA gene abundances or NPR, 50 mg L-1AgNPs significantly decreased AOB amoA gene abundance (up to 76% over 14 days), and significantly decreased NPR by 20-fold in low-salinity sediments and by twofold in mesohaline sediments, after one day. AgNP behaviour differed between sites, whereby greater aggregation occurred in mesohaline waters (possibly due to higher salinity), which may have reduced toxicity. In conclusion, AgNPs have the potential to reduce ammonia oxidation in estuarine sediments, particularly where AgNPs accumulate over time and reach high concentrations. This could lead to long-term risks to nitrification, especially in polyhaline estuaries where ammonia-oxidation is largely driven by AOB.
authors.affiliation: School of Biological Sciences, University of Essex, Essex, CO4 3SQ, UK.
authors.forename: Jessica
authors.initials: J
authors.lastname: Beddow
authors.affiliation: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Björn
authors.initials: B
authors.lastname: Stolpe
authors.affiliation: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Paula A
authors.initials: PA
authors.lastname: Cole
authors.affiliation: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.|Center for Environmental NanoScience and Risk, University of South Carolina, Columbia, SC, 29028, USA.
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Lead
authors.affiliation: Institute of Population Genetics, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine University, Düsseldorf, 40225, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Sapp
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, The Nothe, Barrack Road, Weymouth, Dorset, DT4 8UB, UK.
authors.forename: Brett P
authors.initials: BP
authors.lastname: Lyons
authors.affiliation: School of Biological Sciences, University of Essex, Essex, CO4 3SQ, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Colbeck
authors.affiliation: School of Biological Sciences, University of Essex, Essex, CO4 3SQ, UK.
authors.forename: Corinne
authors.initials: C
authors.lastname: Whitby
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001105:Archaea / Q000235:genetics / Q000378:metabolism; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D063366:Estuaries; D019766:Genes, Archaeal; D005798:Genes, Bacterial; D019015:Geologic Sediments / Q000382:microbiology*; D053768:Metal Nanoparticles / Q000633:toxicity*; D058465:Nitrification / Q000187:drug effects*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics*; D054712:Salinity; D012834:Silver / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase