title: Large-scale controls on potential respiration and denitrification in riverine floodplains.
abstract: Restoration measures of deteriorated river ecosystems generally aim at increasing the spatial heterogeneity and connectivity of these systems in order to increase biodiversity and ecosystem stability. While this is believed to benefit overall ecological integrity, consequences of such restoration projects on biogeochemical processes per se (i.e. ecosystem functioning) in fluvial systems are rarely considered. We address these issues by evaluating the characteristics of surface water connection between side arms and the main river channel in a former braided river section and the role and degree of connectivity (i.e. duration of surface water connection) on the sediment biogeochemistry. We hypothesized that potential respiration and denitrification would be controlled by the degree of hydrological connectivity, which was increased after floodplain restoration. We measured potential microbial respiration (SIR) and denitrification (DEA) and compared a degraded floodplain section of the Danube River with a reconnected and restored floodplain in the same river section. Re-establishing surface water connection altered the controls on sediment microbial respiration and denitrification ultimately impacting potential microbial activities. Meta-variables were created to characterize the effects of hydrology, morphology, and the available carbon and nutrient pools on potential microbial processing. Mantel statistics and path analysis were performed and demonstrate a hierarchy where the effects of hydrology on the available substrates and microbial processing are mediated by the morphology of the floodplain. In addition, these processes are highest in the least connected sites. Surface water connection, mediated by morphology regulates the potential denitrification rate and the ratio of N2O to N2emissions, demonstrating the effects of restoration in floodplain systems.
authors.affiliation: Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Max - Emanuelstrasse 17 1190 Vienna, Austria ; WasserCluster Lunz, Inter-university Center for Aquatic Ecosystem Research, Dr. Carl Kupelwieser Promenade 5 3293 Lunz am See, Austria.
authors.forename: Nina
authors.initials: N
authors.lastname: Welti
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bondar-Kunze
authors.forename: Gabriel
authors.initials: G
authors.lastname: Singer
authors.forename: Michael
authors.initials: M
authors.lastname: Tritthart
authors.forename: Sophie
authors.initials: S
authors.lastname: Zechmeister-Boltenstern
authors.forename: Thomas
authors.initials: T
authors.lastname: Hein
authors.forename: Gilles
authors.initials: G
authors.lastname: Pinay
keywords: Connectivity; Danube River; Denitrification enzyme activity; Floodplain restoration; Path analysis; Substrate induced respiration
references.citation: Environ Manage. 2001 Dec;28(6):805-17
references.pmid: 11915968
references.citation: Appl Environ Microbiol. 2000 Sep;66(9):3891-7
references.pmid: 10966405
references.citation: Environ Model Softw. 2011 Sep;26(9):1097-1111
references.pmid: 27667961
references.citation: Ecol Appl. 2006 Dec;16(6):2123-42
references.pmid: 17205892
references.citation: Ecology. 2008 Jun;89(6):1733-43
references.pmid: 18589537
references.citation: Ecol Appl. 2007 Dec;17(8):2365-76
references.pmid: 18213975
references.citation: Trends Ecol Evol. 1996 Jun;11(6):239-42
references.pmid: 21237825
references.citation: Trends Ecol Evol. 2006 Feb;21(2):96-103
references.pmid: 16701481
references.citation: Sci Total Environ. 2004 Jul 26;328(1-3):207-18
references.pmid: 15207585
references.citation: Nature. 2008 Mar 13;452(7184):202-5
references.pmid: 18337819
references.citation: Fresenius J Anal Chem. 2001 Jun;370(2-3):224-8
references.pmid: 11451241
references.citation: Environ Manage. 2002 Oct;30(4):481-91
references.pmid: 12481915