Nitrogen and phosphorus retention estimated independently by flux measurements and dynamic modelling in the estuary, Randers Fjord, Denmark

Nielsen, Kurt; Risgaard-Petersen, Nils; Sømod, Bent; Rysgaard, Søren; Bergø, Tony

doi:10.3354/meps219025

Cited by 50 publications

(49 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The highest daily value in Gullmar Fjord (ϳ0.4 mmol N m Ϫ2 d Ϫ1 ) roughly equals the mean value for a number of Danish shallow fjords (ϳ0.6 mmol N m Ϫ2 d Ϫ1 , recalculated from annual values given by Dalsgaard et al (1999) and Nielsen et al (2001)). The denitrification rates at 10-15 m in Gullmar Fjord were only ϳ20-30% of those measured in situ by the N 2 /Ar method (1.2-2 mmol m Ϫ2 d Ϫ1 ) in sandy mid-Atlantic shelf sediments at 11-15 m in May and September (Laursen and Seitzinger 2002), and they were within the lower range of rates for other temperate continental shelves ( itive correlation between D tot and the C (r ϭ 0.567, P Ͻ 0.05) and N (r ϭ 0.560, P Ͻ 0.05) contents of the sediment also support this interpretation.…”

Section: Autotrophy and Heterotrophy Along The Depth Gradient-supporting

confidence: 53%

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Sundbäck

Linares

Larson

et al. 2004

Limnology & Oceanography

131

View full text Add to dashboard Cite

In littoral sediments, microphytobenthic (MPB) nitrogen assimilation often exceeds nitrogen removal by denitrification, partly because MPB activity suppresses denitrification. Little is known about the balance between these two processes at sublittoral depths. Benthic pigment composition, light and dark oxygen, and nutrient fluxes (NO 3 Ϫ , NH 4 ϩ , dissolved organic nitrogen (DON), PO , Si(OH) 4 ), as well as denitrification were measured between 1 and 3Ϫ 4 15 m in depth in Gullmar Fjord (Skagerrak) in spring and autumn. The hypothesis was that the assimilation/ denitrification ratio would decrease with depth, along with decreasing MPB activity caused by light limitation. MPB photosynthesis occurred along the entire depth gradient, although sediments were net autotrophic only above 5 m. Inorganic nitrogen (DIN) (and silica) flux changed along the depth gradient, the general pattern being sediment uptake at Յ5 m and efflux at Ն10 m depth. DON flux (ϳ50% of total dissolved nitrogen flux) showed a less clear pattern. Two trends regarding DIN fluxes and denitrification-significant light effects and negative correlations with gross primary productivity-showed that MPB activity influenced nitrogen (N) turnover. Although denitrification increased with depth, rates remained low (Ͻ0.4 mmol N m Ϫ2 d Ϫ1 ), and MPB assimilation (0.2-3.6 mmol N m Ϫ2 d Ϫ1 ) exceeded or equaled denitrification. MPB incorporated ϳ35% of the remineralized N along the depth gradient, whereas denitrification removed ϳ20%. Thus, the influence of MPB on benthic nitrogen turnover, denitrification included, extends to sublittoral depths. Further, denitrification does not necessarily remove more N in the deeper, heterotrophic part of the photic zone, compared to the littoral, autotrophic zone.

show abstract

Section: Autotrophy and Heterotrophy Along The Depth Gradient-supporting

confidence: 53%

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Sundbäck

Linares

Larson

et al. 2004

Limnology & Oceanography

131

View full text Add to dashboard Cite

show abstract

“…For this set of data, the reported irradiance ranged between 2 and 1,300 mol photons m Ϫ2 s Ϫ1 . Denitrification was measured by the 15 N isotope pairing technique (Nielsen 1992;Risgaard-Petersen and Rysgaard 1995) and separated into coupled nitrification-denitrification (Dn) and denitrification of bottom-water NO (DW) as de-Ϫ 3 scribed by Nielsen (1992). For a detailed description of the sampling and incubation procedures applied, see the primary sources listed in Table 1.…”

Section: Methodsmentioning

confidence: 99%

“…Denitrification measurements: Denitrification was measured using the 15 N isotope pairing technique (Nielsen 1992): 15 N-labeled NO was added to the water in the reservoirs iglas tubes was replaced with reservoir water. Following an equilibrium period of ϳ4 : 1 h LD (Dalsgaard et al 2000b), the Plexiglas tubes were sealed and incubation was initiated.…”

Section: Btsimentioning

confidence: 99%

“…The investigation is based on analysis of field data from 18 European estuaries collected over the past 10 yr. In this dataset, denitrification activity was measured with the isotope pairing technique (Nielsen 1992)-a technique that allows quantification of and distinction between the dependency of denitrification on bottom-water NO and on NO Ϫ Ϫ 3 3 produced by sedimentary nitrification, respectively. Interpretation of results from analysis of nonexperimental data can be complicated because of interference from both measured and unmeasured covariables.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Coupled nitrification‐denitrification in autotrophic and heterotrophic estuarine sediments: On the influence of benthic microalgae

Risgaard‐Petersen¹

2003

Limnology & Oceanography

200

View full text Add to dashboard Cite

Field data obtained from 18 European estuaries using the isotope pairing technique were analyzed for trends in relationship between activity of benthic microalgae and coupled nitrification-denitrification. Kruskal-Wallis tests and analyses of covariance performed on the field dataset showed strong statistical evidence for the hypothesis that sediments colonized by microalgae whose activity exceeds community respiration display lower rates of coupled nitrification-denitrification than do heterotrophic sediments. In fully heterotrophic sediments, 90% of the measurements fell within the range 0-92 mol N m Ϫ2 h Ϫ1 with a median of 20.3 mol N m Ϫ2 h Ϫ1. In highly autotrophic sediments, 90% of the measurements fell within the range 0-34 mol N m Ϫ2 h Ϫ1 , and the median was 4.2 mol N m Ϫ2 h Ϫ1 . The hypothesis was tested experimentally using 15 N and microsensor (NO ) techniques in prepared Ϫ 3 microcosms with and without algal activity. The results of the experimental studies were consistent with the hypothesis derived from the field data analysis. For the 15 N study, coupled nitrification-denitrification in alga-colonized sediments was between 4 and 51% of the activity in sediments without algae activity, depending on the N load. For the microsensor study, there was no indication of net NO production in alga-colonized sediments before furthermore showed that compared to heterotrophic sediment, the presence of active microalgae might reduce the population of nitrifying bacteria capable of having an active metabolism. These bacterial populations could display diurnal variations in activity correlated with the diurnal variations in O 2 penetration depth, however. The results showed that induction of nitrogen limitation of the nitrifying bacteria population is a major controlling mechanism of coupled nitrification-denitrification in alga-colonized sediments.

show abstract

“…During this state, strong salinity, pH and other physico-chemical gradients near the freshwater front increase the potential effects of geochemical processes such as adsorption/desorption and flocculation, contributing to the removal of sediment, organic matter and associated inorganic nutrients (Eyre and Twigg, 1997;Nielsen et al, 2001). The lower turbulence in the vicinity of the freshwater front allows catchment-derived sediment and organic matter to settle from the water column, the extent of deposition depending on factors such as land-use and catchment geology, the timing and size of the flow event, particle size, current velocities, and the position of the freshwater front, which is primarily influenced by river inflow and the tidal phase.…”

Section: Freshwater Pulsed/recoverymentioning

confidence: 99%

Extension of a qualitative model on nutrient cycling and transformation to include microtidal estuaries on wave-dominated coasts: Southern hemisphere perspective

Taljaard

Niekerk

Joubert

2009

Estuarine, Coastal and Shelf Science

View full text Add to dashboard Cite

Estuaries are dynamic transition zones acting as filters and transformers of nutrients passing from catchments to the sea. We propose an extension to an existing southern hemisphere model on nutrient dynamics in estuaries to include the relatively constricted, microtidal estuaries located along wave-dominated coasts in the region, specifically focusing on the limiting macronutrients nitrogen (N) and phosphorus (P) and on key processes, including physical (e.g. flushing, mixing and sedimentation), geochemical (e.g. flocculation), biochemical (e.g. remineralisation) and biological (e.g. primary production) processes. A simplified model of the physical states (primarily controlled by hydrological characteristics) is used as the basis for the qualitative model, where these are defined in terms of characteristic salinity-induced stratification of the water column, flushing time and the mouth condition.Four physical states are identified: a freshwater-dominated state, freshwater pulsed/recovery state, marine-dominated state and the closed mouth state. The states and their physical characteristics largely resemble that of the earlier model, except that the extended model reflects the dynamics of restricted inlets and introduces the closed mouth state. This model specifically explores the variation within southern African estuarine systems to better inform research and management programmes on the appropriate trophic, temporal and spatial scales at which uncertainties in ecosystem functioning need resolving. It can also be applied to other regions in the southern hemisphere, and even the northern hemisphere, with similar hydrological and estuarine geomorphological characteristics (e.g. the Mediterranean coast, the west coasts of North and South America, and the south-west and south-eastern coasts of Australia).

show abstract

Nitrogen and phosphorus retention estimated independently by flux measurements and dynamic modelling in the estuary, Randers Fjord, Denmark

Cited by 50 publications

References 46 publications

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Coupled nitrification‐denitrification in autotrophic and heterotrophic estuarine sediments: On the influence of benthic microalgae

Extension of a qualitative model on nutrient cycling and transformation to include microtidal estuaries on wave-dominated coasts: Southern hemisphere perspective

Contact Info

Product

Resources

About