scholarly journals Nitrogen regeneration and dissolved organic nitrogen release during spring in a NW Mediterranean coastal zone (Gulf of Lions):implications for the estimation of new production

2000 ◽  
Vol 197 ◽  
pp. 51-65 ◽  
Author(s):  
F Diaz ◽  
P Raimbault
Keyword(s):  
Coastal Zone ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Nitrogen Release ◽  
New Production ◽  
Gulf Of Lions ◽  
Nw Mediterranean

Nitrogen Uptake, Dissolved Organic Nitrogen Release, and New Production

Science ◽  
1994 ◽  
Vol 265 (5180) ◽  
pp. 1843-1846 ◽  
Author(s):  
D. A. Bronk ◽  
P. M. Glibert ◽  
B. B. Ward
Keyword(s):  
Nitrogen Uptake ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Nitrogen Release ◽  
New Production

scholarly journals Nitrogen Release in Pristine and Drained Peat Profiles in Response to Water Table Fluctuations: A Mesocosm Experiment

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Merjo P. P. Laine ◽  
Rauni Strömmer ◽  
Lauri Arvola
Keyword(s):  
Water Table ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Mesocosm Experiment ◽  
Nitrogen Release ◽  
Hydrological Conditions ◽  
Water Table Fluctuations ◽  
Drying And Rewetting ◽  
Response To Water ◽  
Artificial Water

In the northern hemisphere, variability in hydrological conditions was suggested to increase as a consequence of climate warming, which may result in longer droughts than the area has experienced before. Due to their predominately anoxic conditions, peatlands are expected to respond to changes in hydrological conditions, such as successive drying and rewetting periods. As peatlands are rich in organic matter, any major changes in water table may influence the decomposition of it. The hydrological conditions may also influence release of nutrients from peat profiles as well as affect their transport to downstream ecosystems. In our mesocosm experiment, artificial water table fluctuations in pristine peat profiles caused an increase in dissolved organic nitrogen (DON) and ammonium(NH4+-N)concentrations, while no response was found in drained peat profiles, although originating from the same peatland complex.

scholarly journals Dinitrogen fixation and dissolved organic nitrogen fueled primary production and particulate export during the VAHINE mesocosms experiment (New Caledonia lagoon)

2015 ◽  
Vol 12 (5) ◽  
pp. 4273-4313 ◽  
Author(s):  
H. Berthelot ◽  
T. Moutin ◽  
S. L'Helguen ◽  
K. Leblanc ◽  
S. Hélias ◽  
...  
Keyword(s):  
Primary Production ◽  
N2 Fixation ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
New Caledonia ◽  
Organic N ◽  
New Production ◽  
N Sources ◽  
P Limitation ◽  
Particle Export

Abstract. In the oligotrophic ocean characterized by nitrate (NO3-) depletion in surface waters, dinitrogen (N2) fixation and dissolved organic nitrogen (DON) can represent significant nitrogen (N) sources for the ecosystem. Here we deployed in New Caledonia large in situ mesocosms in order to investigate (1) the contribution of N2 fixation and DON use to primary production (PP) and particle export and (2) the fate of the freshly produced particulate organic N (PON) i.e. whether it is preferentially accumulated and recycled in the water column or exported out of the system. The mesocosms were fertilized with phosphate (P) in order to prevent P-limitation and promote N2 fixation. The diazotrophic community was dominated by diatoms-diazotrophs associations (DDAs) during the first part of the experiment for 10 days (P1) followed by the unicellular N2-fixing cyanobacteria UCYN-C the 9 last days (P2) of the experiment. N2 fixation rates averaged 9.8 ± 4.0 and 27.7 ± 8.6 nM d−1 during P1 and P2, respectively. NO3- concentrations (< 40 nM) in the mesocosms were a negligible source of N indicating that N2 fixation was the main driver of new production all along the experiment. The contribution of v fixation to PP was not significantly different (p > 0.05) during P1 (9.0 ± 3.3%) and P2 (12.6 ± 6.1%). However, the e ratio that quantifies the efficiency of a system to export particulate organic carbon (POCexport) compared to PP (e ratio = POCexport/PP) was significantly higher (p < 0.05) during P2 (39.7 ± 24.9%) than during P1 (23.9 ± 20.2%) indicating that the production sustained by UCYN-C was more efficient at promoting C export than the production sustained by DDAs. During P1, PON was stable and the total amount of N provided by N2 fixation (0.10 ± 0.02 μM) was not significantly different (p > 0.05) from the total amount of PON exported (0.10 ± 0.04 μM), suggesting a rapid and probably direct export of the recently fixed N2 by the DDAs. During P2, both PON concentrations and PON export increased in the mesocosms by a factor 1.5–2. Unlike in P1, this PON production was not totally explained by the new N provided by N2 fixation. The use of DON, whose concentrations decreased significantly (p < 0.05) from 5.3 ± 0.5 μM to 4.4 ± 0.5 μM, appeared to be the missing N source. The DON consumption of about 0.9 μM during P2 is even higher than the total amount of new N brought by N2 fixation (about 0.25 μM) during the same period. These results suggest that while DDAs mainly rely on N2 fixation for their N requirement, both N2 fixation and DON can be significant N-sources for primary production and particulate export following UCYN-C blooms in the New Caledonia lagoon and by extension in the N-limited Ocean where similar events are likely to occur.

scholarly journals Dinitrogen fixation and dissolved organic nitrogen fueled primary production and particulate export during the VAHINE mesocosm experiment (New Caledonia lagoon)

2015 ◽  
Vol 12 (13) ◽  
pp. 4099-4112 ◽  
Author(s):  
H. Berthelot ◽  
T. Moutin ◽  
S. L'Helguen ◽  
K. Leblanc ◽  
S. Hélias ◽  
...  
Keyword(s):  
Primary Production ◽  
N2 Fixation ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
New Caledonia ◽  
Organic N ◽  
New Production ◽  
N Sources ◽  
P Limitation ◽  
Particle Export

Abstract. In the oligotrophic ocean characterized by nitrate (NO3−) depletion in surface waters, dinitrogen (N2) fixation and dissolved organic nitrogen (DON) can represent significant nitrogen (N) sources for the ecosystem. In this study, we deployed large in situ mesocosms in New Caledonia in order to investigate (1) the contribution of N2 fixation and DON use to primary production (PP) and particle export and (2) the fate of the freshly produced particulate organic N (PON), i.e., whether it is preferentially accumulated and recycled in the water column or exported out of the system. The mesocosms were fertilized with phosphate (PO43-) in order to prevent phosphorus (P) limitation and promote N2 fixation. The diazotrophic community was dominated by diatom–diazotroph associations (DDAs) during the first part of the experiment for 10 days (P1) followed by the unicellular N2-fixing cyanobacteria UCYN-C for the last 9 days (P2) of the experiment. N2 fixation rates averaged 9.8 ± 4.0 and 27.7 ± 8.6 nmol L−1 d−1 during P1 and P2, respectively. NO3− concentrations (< 0.04 μmol L−1) in the mesocosms were a negligible source of N, indicating that N2 fixation was the main driver of new production throughout the experiment. The contribution of N2 fixation to PP was not significantly different (p > 0.05) during P1 (9.0 ± 3.3 %) and P2 (12.6 ± 6.1 %). However, the e ratio that quantifies the efficiency of a system to export particulate organic carbon (POCexport) compared to PP (e ratio = POCexport/PP) was significantly higher (p < 0.05) during P2 (39.7 ± 24.9 %) than during P1 (23.9 ± 20.2 %), indicating that the production sustained by UCYN-C was more efficient at promoting C export than the production sustained by DDAs. During P1, PON was stable and the total amount of N provided by N2 fixation (0.10 ± 0.02 μmol L−1) was not significantly different (p > 0.05) from the total amount of PON exported (0.10 ± 0.04 μmol L−1), suggesting a rapid and probably direct export of the recently fixed N2 by the DDAs. During P2, both PON concentrations and PON export increased in the mesocosms by a factor 1.5–2. Unlike in P1, this PON production was not totally explained by the new N provided by N2 fixation. The use of DON, whose concentrations decreased significantly (p < 0.05) from 5.3 ± 0.5 μmol L−1 to 4.4 ± 0.5 μmol L−1, appeared to be the missing N source. The DON consumption (~ 0.9 μmol L−1) during P2 is higher than the total amount of new N brought by N2 fixation (~ 0.25 μmol L−1) during the same period. These results suggest that while DDAs mainly rely on N2 fixation for their N requirements, both N2 fixation and DON can be significant N sources for primary production and particulate export following UCYN-C blooms in the New Caledonia lagoon and by extension in the N-limited oceans where similar events are likely to occur.

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