Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes

removal versus recycling of biologically available N

Anne Uldahl, Gary Thomas Banta, Eva Boegh, Anne Giblin

Research output: Contribution to conferenceConference abstract for conferenceResearch

Abstract

Nitrate present or generated in any benthic ecosystem can be reduced by a number of microbial pathways, most notably denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA). The first two processes remove of biologically available N from the ecosystem in the form of gaseous N2, while the last process transforms of NO3- to another biologically available form, NH4+, and thus merely recycles N. Salt marshes are important ecosystems for the cycling, retention and removal of biologically available N transported from land to the oceans. We used ongoing ecosystem level nutrient additions experiments in two New England salt marshes, Plum Island Sound (NO3- additions since 2003) and Great Sippewissett Marsh (fertilizer additions since the 1970's) to examine the relative importance of these NO3- reduction pathways in salt marshes. Sediments from several experimental (and unmanipulated) sites were collected during the late summer/fall of 2009 and summer 2010 to measure the potential rates of NO3- reduction in sediment slurries enriched with NO3- and 15NO3- added as a tracer. The resulting 15N-labeled products (30N2, 29N2 and 15NH4+) were analyzed by mass spectrometry to determine rates of denitrification, anammox and DNRA, respectively. Sediment and plant parameters were also assessed for each site. Potential denitrification rates were high during mid-summer (up to 30 nmol N gww-1 h-1) but low during late summer and fall (< 5 nmol N gww-1 h-1). DNRA rates were both seasonally and spatially variable but was the dominant reduction pathway when denitrification was low suggesting a shift in importance between these two processes. This shift was loosely related to increasing NO3- loadings in Plum Island Sound, but showed the opposite trend in relation to N loading in Sippewissett. Clearly more work is needed to understand what determines the relative importance of removal versus recycling processes in salt marsh ecosystems.
Original languageEnglish
Publication dateNov 2011
Number of pages1
Publication statusPublished - Nov 2011
Event21st Biennial Conference of the Coastal and Estuarine Research Federation - Ocean Center, Daytona Beach, United States
Duration: 6 Nov 201110 Nov 2011
http://www.sgmeet.com/cerf2011/

Conference

Conference21st Biennial Conference of the Coastal and Estuarine Research Federation
LocationOcean Center
CountryUnited States
CityDaytona Beach
Period06/11/201110/11/2011
Internet address

Cite this

Uldahl, A., Banta, G. T., Boegh, E., & Giblin, A. (2011). Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes: removal versus recycling of biologically available N. Abstract from 21st Biennial Conference of the Coastal and Estuarine Research Federation, Daytona Beach, United States.
Uldahl, Anne ; Banta, Gary Thomas ; Boegh, Eva ; Giblin, Anne. / Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes : removal versus recycling of biologically available N. Abstract from 21st Biennial Conference of the Coastal and Estuarine Research Federation, Daytona Beach, United States.1 p.
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author = "Anne Uldahl and Banta, {Gary Thomas} and Eva Boegh and Anne Giblin",
year = "2011",
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Uldahl, A, Banta, GT, Boegh, E & Giblin, A 2011, 'Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes: removal versus recycling of biologically available N' 21st Biennial Conference of the Coastal and Estuarine Research Federation, Daytona Beach, United States, 06/11/2011 - 10/11/2011, .

Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes : removal versus recycling of biologically available N. / Uldahl, Anne; Banta, Gary Thomas; Boegh, Eva; Giblin, Anne.

2011. Abstract from 21st Biennial Conference of the Coastal and Estuarine Research Federation, Daytona Beach, United States.

Research output: Contribution to conferenceConference abstract for conferenceResearch

TY - ABST

T1 - Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes

T2 - removal versus recycling of biologically available N

AU - Uldahl, Anne

AU - Banta, Gary Thomas

AU - Boegh, Eva

AU - Giblin, Anne

PY - 2011/11

Y1 - 2011/11

N2 - Nitrate present or generated in any benthic ecosystem can be reduced by a number of microbial pathways, most notably denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA). The first two processes remove of biologically available N from the ecosystem in the form of gaseous N2, while the last process transforms of NO3- to another biologically available form, NH4+, and thus merely recycles N. Salt marshes are important ecosystems for the cycling, retention and removal of biologically available N transported from land to the oceans. We used ongoing ecosystem level nutrient additions experiments in two New England salt marshes, Plum Island Sound (NO3- additions since 2003) and Great Sippewissett Marsh (fertilizer additions since the 1970's) to examine the relative importance of these NO3- reduction pathways in salt marshes. Sediments from several experimental (and unmanipulated) sites were collected during the late summer/fall of 2009 and summer 2010 to measure the potential rates of NO3- reduction in sediment slurries enriched with NO3- and 15NO3- added as a tracer. The resulting 15N-labeled products (30N2, 29N2 and 15NH4+) were analyzed by mass spectrometry to determine rates of denitrification, anammox and DNRA, respectively. Sediment and plant parameters were also assessed for each site. Potential denitrification rates were high during mid-summer (up to 30 nmol N gww-1 h-1) but low during late summer and fall (< 5 nmol N gww-1 h-1). DNRA rates were both seasonally and spatially variable but was the dominant reduction pathway when denitrification was low suggesting a shift in importance between these two processes. This shift was loosely related to increasing NO3- loadings in Plum Island Sound, but showed the opposite trend in relation to N loading in Sippewissett. Clearly more work is needed to understand what determines the relative importance of removal versus recycling processes in salt marsh ecosystems.

AB - Nitrate present or generated in any benthic ecosystem can be reduced by a number of microbial pathways, most notably denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA). The first two processes remove of biologically available N from the ecosystem in the form of gaseous N2, while the last process transforms of NO3- to another biologically available form, NH4+, and thus merely recycles N. Salt marshes are important ecosystems for the cycling, retention and removal of biologically available N transported from land to the oceans. We used ongoing ecosystem level nutrient additions experiments in two New England salt marshes, Plum Island Sound (NO3- additions since 2003) and Great Sippewissett Marsh (fertilizer additions since the 1970's) to examine the relative importance of these NO3- reduction pathways in salt marshes. Sediments from several experimental (and unmanipulated) sites were collected during the late summer/fall of 2009 and summer 2010 to measure the potential rates of NO3- reduction in sediment slurries enriched with NO3- and 15NO3- added as a tracer. The resulting 15N-labeled products (30N2, 29N2 and 15NH4+) were analyzed by mass spectrometry to determine rates of denitrification, anammox and DNRA, respectively. Sediment and plant parameters were also assessed for each site. Potential denitrification rates were high during mid-summer (up to 30 nmol N gww-1 h-1) but low during late summer and fall (< 5 nmol N gww-1 h-1). DNRA rates were both seasonally and spatially variable but was the dominant reduction pathway when denitrification was low suggesting a shift in importance between these two processes. This shift was loosely related to increasing NO3- loadings in Plum Island Sound, but showed the opposite trend in relation to N loading in Sippewissett. Clearly more work is needed to understand what determines the relative importance of removal versus recycling processes in salt marsh ecosystems.

KW - nitrogen

KW - salt marsh

KW - nutrient cycling

M3 - Conference abstract for conference

ER -

Uldahl A, Banta GT, Boegh E, Giblin A. Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes: removal versus recycling of biologically available N. 2011. Abstract from 21st Biennial Conference of the Coastal and Estuarine Research Federation, Daytona Beach, United States.