DON as a source of bioavailable nitrogen for phytoplankton

Bronk, Deborah A.; See, Jason; Bradley, Paul B.; Killberg, L.

doi:10.5194/bg-4-283-2007

Cited by 437 publications

(261 citation statements)

References 169 publications

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“…Such an evolution is in agreement with an increase in ammonium availability in a decaying bloom (Sambrotto and Mace, 2000;Cochlan, 2008). Note that our f ratios are most probably overestimated because they do not take into account the assimilation of dissolved organic nitrogen by phytoplankton (Bronk et al, 2007). However, we note that urea uptake, a proxy for dissolved organic N assimilation, is usually relatively low south of the polar front, where dissolved inorganic N is abundant (Waldron et al, 1995;Sambrotto and Mace, 2000;Savoye et al, 2004).…”

Section: Upper-ocean N Cycling: High F Ratios and Nitrification Ratessupporting

confidence: 63%

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

et al. 2015

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Abstract. Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO − 3 and NH + 4 ), and nitrification rates were measured at eight stations in austral spring 2011 (October-November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m −2 d −1 and up to 0.31 d −1 respectively) compared to the HNLC reference site (12 mmol C m −2 d −1 and 0.06 d −1 respectively). Primary production was mainly sustained by nitrate uptake, with f ratios (corresponding to NO − 3 -uptake / (NO − 3 -uptake + NH + 4 -uptake)) lying at the upper end of the observations for the Southern Ocean (up to 0.9). We report high rates of nitrification (up to ∼ 3 µmol N L −1 d −1 , with ∼ 90 % of them < 1 µmol N L −1 d −1 ) typically occurring below the euphotic zone, as classically observed in the global ocean. The specificity of the studied area is that at most of the stations, the euphotic layer was shallower than the mixed layer, implying that nitrifiers can efficiently compete with phytoplankton for the ammonium produced by remineralization at low-light intensities. Nitrate produced by nitrification in the mixed layer below the euphotic zone is easily supplied to the euphotic zone waters above, and nitrification sustained 70 ± 30 % of the nitrate uptake in the productive area above the Kerguelen Plateau. This complicates estimations of new production as potentially exportable production. We conclude that high productivity in deep mixing system stimulates the N cycle by increasing both assimilation and regeneration.

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Section: Upper-ocean N Cycling: High F Ratios and Nitrification Ratessupporting

confidence: 63%

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

et al. 2015

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“…The bioavailability of atmospheric organic nitrogen is largely determined by its chemical composition. Specifically, most reduced organic nitrogen species (e.g., amino acids, urea, and amines) can be taken up by marine microorganisms on very short timescales, whereas the organic nitrogen associated with humic-like substances is probably refractory (Bronk et al, 2007). Incubation experiments estimate the bioavailability of atmospheric organic nitrogen to be 20-80 % (Peierls and Paerl, 1997;Seitzinger and Sanders, 1999;Wedyan et al, 2007).…”

Section: Biogeochemical Implicationsmentioning

confidence: 99%

“…30 % on average) (Jickells, 2006;Cape et al, 2011;Cornell, 2011). Indeed, the growing weight of evidence from global observational studies suggests that a considerable fraction of deposited nitrogen is in organic form (Cornell, 2011, and references therein), which is able to stimulate the productivity of bacteria and phytoplankton in the receiving marine ecosystems (Seitzinger and Sanders, 1999;Bronk et al, 2007). In particular, atmospheric organic nitrogen deposition was shown to be especially high over Asia (Cornell, 2011;Ito et al, 2014), implying it is imperative to incorporate this fraction into the budget of atmospheric nitrogen input to the EJS.…”

Section: Introductionmentioning

confidence: 99%

Sources and fluxes of organic nitrogen in precipitation over the southern East Sea/Sea of Japan

Yan

Kim

2015

Atmos. Chem. Phys.

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Abstract. We measured total dissolved reactive nitrogen in precipitation samples collected at Uljin, a Korean coastal site upwind of the southern East Sea/Sea of Japan (EJS), selected as a representative study site of atmospheric deposition over the northwestern Pacific margin. NO − 3 was found to be the most abundant nitrogen species, followed by NH + 4 and dissolved organic nitrogen (DON). Air-mass back-trajectory (AMBT) analysis revealed that a significant fraction of the inorganic nitrogen (NO − 3 and NH + 4 ) originated from mainland Asia, whereas the DON was primarily derived from Korea. Using varimax-rotated factor analysis in combination with major ions as tracers, agricultural activities in Korea were identified as the primary sources of DON in these samples. In addition, a positive correlation was found at Uljin between the size of organic fraction in total reactive nitrogen and nitrogen to carbon atomic ratio in organic matter. This correlation has also been observed at other locations worldwide, implying the utilization potential of atmospheric organic nitrogen might increase with its proportion in total nitrogen. Combining wet deposition measurements in this study with literature values for dry deposition observed at a remote island in the EJS, the total atmospheric depositional flux of reactive nitrogen was estimated to be 115 mmol N m −2 yr −1 over the southern EJS. Our study sheds new light on the potentially significant contribution to primary productivity of the northwestern Pacific Ocean by atmospheric deposition of nitrogen, especially the organic fraction.

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“…We did not explicitly represent the labile fraction of DOP and DON in our model. We assume that the labile part was instantaneously remineralized into the inorganic form resulting in algal-bacterial competition for both N (Kirchman, 1994;Bronk et al, 2007), and P Thingstad, 2005).…”

Section: Overviewmentioning

confidence: 99%

Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?

2011

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Abstract. The biogeochemistry of carbon and nutrients (N,P) in the surface layer of the ocean strongly depends on the complex interactions between primary producers (phytoplankton) and remineralizers (heterotrophic bacteria). To understand how these interactions impact the overall DOC dynamics in the surface layer of the Mediterranean Sea, we implemented, using Eco3M (Ecological Mechanistic Modular Modelling tool), a multi-element model with a mechanistic description of primary production. We studied the model steady state results under various nutrient conditions and fixed cell abundances. By doing so, we show how the bottom up control of osmotrophs growth can impact the overall DOC dynamics in the system. Based on our set of parameters, the biogeochemical characteristics displayed by the model appear realistic when compared to literature data for the Mediterranean basin. Differences in DOC dynamics between N and P limited systems in the model, lead to the conclusion that the unusually high N:P ratio of the Mediterranean Sea may favour the uncoupling between growth and carbon production leading to higher DOC accumulation compared to systems with lower N:P ratio.

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DON as a source of bioavailable nitrogen for phytoplankton

Cited by 437 publications

References 169 publications

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

Sources and fluxes of organic nitrogen in precipitation over the southern East Sea/Sea of Japan

Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?

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