title: Addition of trace metals increases denitrification rate in closed marine systems.
abstract: We investigated the effect of trace metals (Fe, Mn, Cu, Zn and Mo) on the denitrification unit at the Montreal Biodome. Two dosages of the five trace metals were tested on a denitrifying bacterial population which was extracted from the denitrification unit and cultured in 250 mL chemostats with artificial seawater. The low dosage showed a 20% increase in the denitrification rate whereas the high dosage had a more pronounced effect with a 250% increase. No increase in bacterial growth was observed, suggesting that the trace metals had an effect on the denitrification activity. When the trace metals were tested separately, only iron had a significant effect similar to the increase in the denitrification rate observed when the five trace metals were added. The combination of Fe and Mn caused a small but significant increase compared to the five trace metals. We then tested the effect of adding Fe, Mn and Cu to the denitrification unit at the Montreal Biodome. A high dosage of these trace metals showed a 250% increase in the denitrification rate, which went from 200 to 700 g NO(x)-N/d. Our results showed that the addition of trace metals is crucial for denitrification activities.
authors.affiliation: INRS-Institut Armand-Frappier, 531 boul des Prairies, Laval, Canada H7V 1B7.
authors.forename: Normand
authors.initials: N
authors.lastname: Labbé
authors.forename: Serge
authors.initials: S
authors.lastname: Parent
authors.forename: Richard
authors.initials: R
authors.lastname: Villemur
mesh_terms: D017753:Ecosystem; D008954:Models, Biological; D017672:Nitrogen Compounds / Q000302:isolation & purification*; D012623:Seawater / Q000737:chemistry*; D013997:Time Factors; D014131:Trace Elements / Q000737:chemistry*; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
chemical_list: D017672:Nitrogen Compounds; D014131:Trace Elements