Quantity and quality of organic matter (detritus) drives N<sub>2</sub> effluxes (net denitrification) across seasons, benthic habitats, and estuaries

Eyre, Bradley D.; Maher, Damien T.; Squire, Peter

doi:10.1002/2013gb004631

Cited by 91 publications

(80 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast, the organic content differed sig-nificantly between the sediment types. Similar to the sediment O 2 dynamics, the same denitrification rates at different organic contents imply that not all of the organic matter in the sediment could be utilized by the denitrifying bacteria and that not only organic matter quantity but also quality needs to be considered (Hietanen & Kuparinen 2008, Eyre et al 2013, Bonaglia et al 2017). This was also indicated by the lack of correlation of LOI with total denitrification, Dn or Dw.…”

Section: Denitrification In An Oligotrophic Estuarymentioning

confidence: 97%

Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate

Hellemann¹,

Tallberg²,

Bartl

et al. 2017

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

Estuaries are often seen as natural filters of riverine nitrate, but knowledge of this nitrogen sink in oligotrophic systems is limited. We measured spring and summer dinitrogen production (denitrification, anammox) in muddy and non-permeable sandy sediments of an oligotrophic estuary in the northern Baltic Sea, to estimate its function in mitigating the riverine nitrate load. Both sediment types had similar denitrification rates, and no anammox was detected. In spring at high nitrate loading, denitrification was limited by likely low availability of labile organic carbon. In summer, the average denitrification rate was ~138 μmol N m. The corresponding estuarine nitrogen removal for August was ~1.2 t, of which ~93% was removed by coupled nitrification−denitrification. Particulate matter in the estuary was mainly phytoplankton derived (> 70% in surface waters) and likely based on the riverine nitrate which was not removed by direct denitrification due to water column stratification. Subsequently settling particles served as a link between the otherwise uncoupled nitrate in surface waters and benthic nitrogen removal. We suggest that the riverine nitrate brought into the oligotrophic estuary during the spring flood is gradually, and with a time delay, removed by benthic denitrification after being temporarily 'trapped' in phytoplankton particulate matter. The oligotrophic system is not likely to face eutrophication from increasing nitrogen loading due to phosphorus limitation. In response, coupled nitrification−denitrification rates are likely to stay constant, which might increase the future export of nitrate to the open sea and decrease the estuary's function as a nitrogen sink relative to the load.

show abstract

Section: Denitrification In An Oligotrophic Estuarymentioning

confidence: 97%

Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate

Hellemann¹,

Tallberg²,

Bartl

et al. 2017

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

show abstract

“…Denitrification is influenced by oxygen concentration, as well as carbon and nitrate availability (Cornwell et al 1999;Ward et al 2009). Field and mesocosm studies (Fulweiler et al 2007(Fulweiler et al , 2013Eyre et al 2013) in Narragansett Bay, RI suggest that both the quality and quantity of available organic carbon may control the balance between these processes. However, rates of these processes have not been measured separately and simultaneously, and heterotrophic N-fixation has not been proven to occur in sediments beyond the observation of N 2 uptake.…”

Section: Introductionmentioning

confidence: 99%

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

Newell

McCarthy

Gardner³

et al. 2016

Estuaries and Coasts

View full text Add to dashboard Cite

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.

show abstract

“…Isotope additions of either 15

{NO}_{3}^{-}

or 15

{NH}_{4}^{+}

are commonly used; the isotope pairing technique (IPT), developed by Nielsen (1992) uses 15

{NO}_{3}^{-}

additions to differentiate between denitrification of nitrate derived from the water column and from coupled nitrification in the surface sediments. Measurements of net N 2 fluxes without isotope additions are also used with both cores and chambers (Ferguson et al ; Smyth et al ; Eyre et al ). Each method has its own strengths and weaknesses ( see Cornwell et al and Steingruber et al for more complete comparisons); however, none of these techniques both preserve conditions in the field and directly account for subsurface rates.…”

mentioning

confidence: 99%

Push‐pull incubation method reveals the importance of denitrification and dissimilatory nitrate reduction to ammonium in seagrass root zone

Aoki

McGlathery

2017

Limnol. Oceanogr. Methods

View full text Add to dashboard Cite

In this study, we developed a push‐pull incubation method to measure denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in subsurface sediments of subtidal seagrass meadows. This subtidal push‐pull technique, adapted from a push‐pull method developed for intertidal salt marshes, used mini‐piezometers to directly sample pore water in the root zone of the seagrass during an in situ incubation. The pore water was amended with 15 NO3− and with Ar(g) as a tracer gas, and the denitrification products (28N2(g), 29N2(g), and 30N2(g)) were measured with membrane inlet mass spectrometry (MIMS), using the Ar tracer to correct for dilution and gas loss. Production of 15 NH4+ was also measured using hypobromite oxidation and MIMS to determine rates of DNRA. Using this new technique, subsurface rates of denitrification and DNRA were determined to be 17.5 μmol N m−2 h−1 and 14.7 μmol N m−2 h−1, respectively, for a restored Zostera meadow. Rates showed substantial spatial variability, likely due to both heterogeneous conditions in the root zone sediment and variable in situ conditions. When compared to traditional core and slurry incubations, push‐pull rates were greater and more variable, suggesting that the push‐pull technique more accurately captures heterogeneity and the natural range of denitrification and DNRA in subsurface sediments under field conditions. In vegetated systems with low water column nitrate concentrations, the majority of denitrification and DNRA occurs below the sediment surface, and the subtidal push‐pull technique provides an effective method to assess these subsurface rates.

show abstract

Quantity and quality of organic matter (detritus) drives N₂ effluxes (net denitrification) across seasons, benthic habitats, and estuaries

Cited by 91 publications

References 74 publications

Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate

Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate

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

Push‐pull incubation method reveals the importance of denitrification and dissimilatory nitrate reduction to ammonium in seagrass root zone

Contact Info

Product

Resources

About

Quantity and quality of organic matter (detritus) drives N2 effluxes (net denitrification) across seasons, benthic habitats, and estuaries

Cited by 91 publications

References 74 publications

Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate

Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate

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

Push‐pull incubation method reveals the importance of denitrification and dissimilatory nitrate reduction to ammonium in seagrass root zone

Contact Info

Product

Resources

About

Quantity and quality of organic matter (detritus) drives N₂ effluxes (net denitrification) across seasons, benthic habitats, and estuaries