title: Effects of planting Phragmites australis on nitrogen removal, microbial nitrogen cycling, and abundance of ammonia-oxidizing and denitrifying microorganisms in sediments.
abstract: We examined the effect of planting an emergent aquatic plant (Phragmites australis) on nitrogen removal from sediments using a 42-d pot experiment. The experimental pot systems comprised two types of sediments planted with and without young P. australis. Total nitrogen (total N), total dissolved N, and NH4-N in the sediments decreased markedly after planting. In contrast, those levels decreased only slightly in the unplanted sediments. The decrease in total N in the P. australis-planted sediments was 7-20 times those in the unplanted sediments. Abundances of bacterial 16S rRNA, archaeal 16S rRNA, ammonia-oxidizing bacterial ammonia monooxygenase (amoA), ammonia-oxidizing archaeal amoA, and denitrifying bacterial nitrite reductase (nirK) genes increased significantly in sediments after planting. Phragmites australis appears to have released oxygen and created a repeating cycle of oxidizing and reducing conditions in the sediments. These conditions should promote mineralization of organic N, nitrification, and denitrification in the sediments. Phragmites australis absorbed bioavailable nitrogen generated by microbial nitrogen metabolism. During the 42-d period after planting, 31-44% of total N was removed by microbial nitrogen cycling, and 56-69% was removed via absorption by P. australis. These results suggest that planting P. australis can increase microbial populations and their activities, and that nitrogen removal can be accelerated by the combined functions of P. australis and microorganisms in the sediment. Thus, planting P. australis has considerable potential as an effective remediation technology for eutrophic sediments.
authors.affiliation: a Department of Research , Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi , 4-3-11 Takeda, Kofu , Yamanashi 400-8511 , Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Toyama
authors.affiliation: b Division of Sustainable Energy and Environmental Engineering , Osaka University , 2-1 Yamadaoka, Suita , Osaka 565-0871 , Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Nishimura
authors.affiliation: c National Institute for Environmental Studies , 16-2 Onogawa, Tsukuba , Ibaraki 305-8506 , Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Ogata
authors.affiliation: d Department of Health Science , School of Allied Health Sciences, Kitasato University , 1-15-1 Kitasato, Sagamihara-Minami , Kanagawa 252-0373 , Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Sei
authors.affiliation: a Department of Research , Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi , 4-3-11 Takeda, Kofu , Yamanashi 400-8511 , Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mori
authors.affiliation: b Division of Sustainable Energy and Environmental Engineering , Osaka University , 2-1 Yamadaoka, Suita , Osaka 565-0871 , Japan.
authors.forename: Michihiko
authors.initials: M
authors.lastname: Ike
keywords: common reed (); microbial nitrogen cycling; nitrogen absorption; nitrogen removal; sediments