Impacts of long-term fertilization on salt marsh tidal creek benthic nutrient and N&lt;sub&gt;2 gas fluxes

Vieillard, Amanda M.; Fulweiler, Robinson W.

doi:10.3354/meps10013

Cited by 30 publications

(27 citation statements)

References 69 publications

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“…However, this relationship was driven entirely by N 2 O flux from the 323 treatment (5.83 6 3.6 lmolÁm À2 Áh À1 ), the same relationship from 0 through 163 was not significant indicating that the sediment community did not respond to nitrate additions until they were much larger than ambient levels. This is consistent with findings suggesting that DNRA may be outcompeting denitrification in nearby salt marsh tidal creeks that have been fertilized with nitrate (Vieillard and Fulweiler 2012). 2a, Table 2).…”

Section: Nutrient Addition Experimentssupporting

confidence: 90%

Tidal pulsing alters nitrous oxide fluxes in a temperate intertidal mudflat

Vieillard

Fulweiler

2014

Ecology

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Environmental pulses, or sudden, marked changes to the conditions within an ecosystem, can be important drivers of resource availability in many systems. In this study, we investigated the effect of tidal pulsing on the fluxes of nitrous oxide (N2O), a powerful greenhouse gas, from a marine intertidal mudflat on the north shore of Massachusetts, USA. We found these tidal flat sediments to be a sink of N2O at low tide with an average uptake rate of -6.7 +/- 2 micromol x m(-2) x h(-1). Further, this N20 sink increased the longer sediments were tidally exposed. These field measurements, in conjunction with laboratory nutrient additions, revealed that this flux appears to be driven primarily by sediment denitrification. Additionally, N2O uptake was most responsive to dissolved inorganic nitrogen with phosphorus (DIN + DIP) addition, suggesting that the N2O consumption process may be P limited. Furthermore, nutrient addition experiments suggest that dissimilatory nitrate reduction to ammonium (DNRA) releases N20 at the highest levels of nitrate fertilization. Our findings indicate that tidal flats are important sinks of N2O, potentially capable of offsetting the release of this potent greenhouse gas by other, nearby ecosystems.

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Section: Nutrient Addition Experimentssupporting

confidence: 90%

Tidal pulsing alters nitrous oxide fluxes in a temperate intertidal mudflat

Vieillard

Fulweiler

2014

Ecology

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“…For this study, Deegan et al 2007 and Koop-Jakobsen and Giblin 2010, nitrate analysis as described in Methods. Vieillard and Fulweiler (2012) analyzed samples on a SEAL Autoanalyzer 3 instead of a Lachat Quik Chem 8000. points along each creek. These transects were at right angles to the creek channel axis and extended landward 50 m from the break between tall S. alterniflora and high marsh S. patens.…”

Section: Experimental Designmentioning

confidence: 99%

Saltmarsh plant responses to eutrophication

Johnson¹,

Warren

Deegan

et al. 2016

Ecological Applications

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Abstract. In saltmarsh plant communities, bottom-up pressure from nutrient enrichment is predicted to increase productivity, alter community structure, decrease biodiversity, and alter ecosystem functioning. Previous work supporting these predictions has been based largely on short-term, plot-level (e.g., 1-300 m 2 ) studies, which may miss landscape-level phenomena that drive ecosystem-level responses. We implemented an ecosystem-scale, nine-year nutrient experiment to examine how saltmarsh plants respond to simulated conditions of coastal eutrophication. Our study differed from previous saltmarsh enrichment studies in that we applied realistic concentrations of nitrate (70-100 μM NO 3 − ), the most common form of coastal nutrient enrichment, via tidal water at the ecosystem scale (~60,000 m 2 creeksheds). Our enrichments added a total of 1,700 kg N·creek −1 ·yr −1 , which increased N loading 10-fold vs. reference creeks (low-marsh, 171 g N·m −2 ·yr −1 ; high-marsh, 19 g N·m −2 ·yr −1 ). Nutrients increased the shoot mass and height of low marsh, tall Spartina alterniflora; however, declines in stem density resulted in no consistent increase in aboveground biomass. High-marsh plants S. patens and stunted S. alterniflora did not respond consistently to enrichment. Nutrient enrichment did not shift community structure, contrary to the prediction of nutrient-driven dominance of S. alterniflora and Distichlis spicata over S. patens. Our mild responses may differ from the results of previous studies for a number of reasons. First, the limited response of the high marsh may be explained by loading rates orders of magnitude lower than previous work. Low loading rates in the high marsh reflect infrequent inundation, arguing that inundation patterns must be considered when predicting responses to estuarine eutrophication. Additionally, we applied nitrate instead of the typically used ammonium, which is energetically favored over nitrate for plant uptake. Thus, the form of nitrogen enrichment used, not just N-load, may be important in predicting plant responses. Overall, our results suggest that when coastal eutrophication is dominated by nitrate and delivered via flooding tidal water, aboveground saltmarsh plant responses may be limited despite moderate-to-high water-column N concentrations. Furthermore, we argue that the methodological limitations of nutrient studies must be considered when using results to inform management decisions about wetlands.

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“…Recent studies indicate that N-fixation (reported as negative values, indicating sediment N 2 uptake) can be a significant N source in coastal sediments (−12 to −250 μmol N m −2 h −1 reported in: Fulweiler et al 2007;Mortazavi et al 2012;McCarthy et al 2015), reservoirs (approx. −200 μmol N m −2 h −1 ; Grantz et al 2012), and tidal flats (−402.7 μmol N m −2 h −1 ; Vieillard and Fulweiler 2012).…”

Section: Introductionmentioning

confidence: 99%

Sediment Nitrogen Fixation: a Call for Re-evaluating Coastal N Budgets

Newell

McCarthy

Gardner³

et al. 2016

Estuaries and Coasts

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Coastal ocean primary productivity is often limited by nitrogen (N) availability, which is determined by the balance between N sources (e.g., N-fixation, groundwater, river inputs, etc.) and sinks (e.g., denitrification, sediment burial, etc.). Historically, heterotrophic N-fixation in sediments was excluded as a significant source of N in estuarine budgets, based on low, indirectly measured rates (e.g., acetylene reduction assay) and because it was unnecessary to achieve mass balance. Many recent studies using net N 2 flux measurements have shown that sediment N-fixation can equal or exceed N 2 loss. In an effort to quantify N 2 production and consumption simultaneously, we measured N-fixation and denitrification directly in sediment cores from a temperate estuary (Waquoit Bay, MA). N-fixation, dissimilatory nitrate reduction to ammonium, and denitrification occurred simultaneously, and the net N 2 flux shifted from uptake (N-fixation) to efflux (denitrification) over the 120-h incubation. Evidence for Nfixation included net 28 N 2 and 30 N 2 uptake, 15 NH 4 + production from 30 N 2 additions, 15 N organic matter production, and nifH expression. N-fixation from 30 N 2 was up to eight times higher than potential denitrification. However, N-fixation calculated from 15 NO 3 − was one half of the measured fixation from 30 N 2 , indicating that 15 NO 3 -isotope labeling calculations may underestimate N-fixation. These results highlight the dynamic nature of sediment N cycling and suggest that quantifying individual processes allows a greater understanding of what net N 2 fluxes signify and how that balance varies over time.

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Impacts of long-term fertilization on salt marsh tidal creek benthic nutrient and N<sub>2 gas fluxes

Cited by 30 publications

References 69 publications

Tidal pulsing alters nitrous oxide fluxes in a temperate intertidal mudflat

Tidal pulsing alters nitrous oxide fluxes in a temperate intertidal mudflat

Saltmarsh plant responses to eutrophication

Sediment Nitrogen Fixation: a Call for Re-evaluating Coastal N Budgets

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