Relationship Between N2-Fixation and Heterocyst Abundance and its Relevance to the Nitrogen Budget of Lake 227

1994 ◽  
Vol 51 (10) ◽  
pp. 2254-2266 ◽  
Author(s):  
D. L. Findlay ◽  
R. E. Hecky ◽  
L. L. Hendzel ◽  
M. P. Stainton ◽  
G. W. Regehr
Keyword(s):  
N:P Ratio ◽  
Molar Ratio ◽  
External Loading ◽  
N Fixation ◽  
Fixation Rate ◽  
Loading Rates ◽  
Relative Contribution ◽  
Cyanobacteria Blooms ◽  
N Loading ◽  
Low Nitrogen

A significant relationship between seasonal N2-fixation rate and heterocyst abundance has been found in Lake 227 and can be modelled to estimate areal rates of N2-fixation based on the known historical phytoplankton records. Experimental imposition of low nitrogen (N): phosphorus (P) loading ratios stimulated N,-fixation. The N:P molar ratio of the internal pool of nutrients oscillates around a mean of 30:1, despite experimental loading ratios that vary from 13:1 to 0. Maintenance of this internal nutrient mass ratio requires preferential regeneration of N through time at all loading rates. Heterocystous, cyanobacteria blooms are most predictable during imposition of a very low external loading N:P ratio and high P loading relative to natural sources. Knowledge of the internal loading N:P ratio and relative contribution of internal and external loadings are required for predicting blooms at intermediate external N:P loading rates. The internal N:P ratio has fluctuated within narrow limits over 25 yr of nearly constant P loading because of adjustments in N2-fixation, N sedimentation, and denitrification, which have counterbalanced changing experimental N loading regimes.

scholarly journals Gluconacetobacter diazotrophicus Pal5 Enhances Plant Robustness Status under the Combination of Moderate Drought and Low Nitrogen Stress in Zea mays L.

2021 ◽  
Vol 9 (4) ◽  
pp. 870
Author(s):  
Muhammad Aammar Tufail ◽  
María Touceda-González ◽  
Ilaria Pertot ◽  
Ralf-Udo Ehlers
Keyword(s):  
Zea Mays ◽  
Plant Growth ◽  
Zea Mays L ◽  
Growth Promotion ◽  
Nitrogen Stress ◽  
Rrna Gene ◽  
N Fixation ◽  
Gluconacetobacter Diazotrophicus ◽  
Maize Plants ◽  
Low Nitrogen

Plant growth promoting endophytic bacteria, which can fix nitrogen, plays a vital role in plant growth promotion. Previous authors have evaluated the effect of Gluconacetobacter diazotrophicus Pal5 inoculation on plants subjected to different sources of abiotic stress on an individual basis. The present study aimed to appraise the effect of G. diazotrophicus inoculation on the amelioration of the individual and combined effects of drought and nitrogen stress in maize plants (Zea mays L.). A pot experiment was conducted whereby treatments consisted of maize plants cultivated under drought stress, in soil with a low nitrogen concentration and these two stress sources combined, with and without G. diazotrophicus seed inoculation. The inoculated plants showed increased plant biomass, chlorophyll content, plant nitrogen uptake, and water use efficiency. A general increase in copy numbers of G. diazotrophicus, based on 16S rRNA gene quantification, was detected under combined moderate stress, in addition to an increase in the abundance of genes involved in N fixation (nifH). Endophytic colonization of bacteria was negatively affected by severe stress treatments. Overall, G. diazotrophicus Pal5 can be considered as an effective tool to increase maize crop production under drought conditions with low application of nitrogen fertilizer.

scholarly journals Nitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal blooms

2018 ◽  
Vol 15 (9) ◽  
pp. 2891-2907 ◽  
Author(s):  
Kateri R. Salk ◽  
George S. Bullerjahn ◽  
Robert Michael L. McKay ◽  
Justin D. Chaffin ◽  
Nathaniel E. Ostrom
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Lake Erie ◽  
N Uptake ◽  
N Fixation ◽  
N Budget ◽  
N2o Production ◽  
N Removal ◽  
Uptake Rates ◽  
N Loading

Abstract. Recent global water quality crises point to an urgent need for greater understanding of cyanobacterial harmful algal blooms (cHABs) and their drivers. Nearshore areas of Lake Erie such as Sandusky Bay may become seasonally limited by nitrogen (N) and are characterized by distinct cHAB compositions (i.e., Planktothrix over Microcystis). This study investigated phytoplankton N uptake pathways, determined drivers of N depletion, and characterized the N budget in Sandusky Bay. Nitrate (NO3-) and ammonium (NH4+) uptake, N fixation, and N removal processes were quantified by stable isotopic approaches. Dissimilatory N reduction was a relatively modest N sink, with denitrification, anammox, and N2O production accounting for 84, 14, and 2 % of sediment N removal, respectively. Phytoplankton assimilation was the dominant N uptake mechanism, and NO3- uptake rates were higher than NH4+ uptake rates. Riverine N loading was sometimes insufficient to meet assimilatory and dissimilatory demands, but N fixation alleviated this deficit. N fixation made up 23.7–85.4 % of total phytoplankton N acquisition and indirectly supports Planktothrix blooms. However, N fixation rates were surprisingly uncorrelated with NO3- or NH4+ concentrations. Owing to temporal separation in sources and sinks of N to Lake Erie, Sandusky Bay oscillates between a conduit and a filter of downstream N loading to Lake Erie, delivering extensively recycled forms of N during periods of low export. Drowned river mouths such as Sandusky Bay are mediators of downstream N loading, but climate-change-induced increases in precipitation and N loading will likely intensify N export from these systems.

Effects of zooplankton and nutrients on phytoplankton: an experimental analysis in a eutrophic tropical reservoir

2017 ◽  
Vol 68 (6) ◽  
pp. 1061 ◽  
Author(s):  
Juliana dos Santos Severiano ◽  
Viviane Lúcia dos Santos Almeida-Melo ◽  
Enaide Marinho de Melo-Magalhães ◽  
Maria do Carmo Bittencourt-Oliveira ◽  
Ariadne do Nascimento Moura
Keyword(s):  
Experimental Analysis ◽  
Phytoplankton Biomass ◽  
Phytoplankton Community ◽  
N:P Ratio ◽  
Molar Ratio ◽  
Zooplankton Species ◽  
Tropical Reservoir ◽  
Total Phytoplankton Biomass ◽  
Taxonomic Class ◽  
Total Phytoplankton

Experiments were conducted to evaluate the N:P ratio, as well as the effects of the interaction between this ratio and zooplankton, on phytoplankton in a tropical reservoir. Three experiments were performed in the presence (+Z) or absence (–Z) of zooplankton and the addition of N and P in different ratios (N:P molar ratio of 5, 16 and 60).In Experiment I, the total phytoplankton biomass and biomass by taxonomic class and species of the N:P 16–Z treatment did not differ significantly from that of the control, whereas for N:P 16+Z, there was a reduction in total phytoplankton. In Experiment II, there was a significant increase in Bacillariophyceae and the biomass of two species in the N:P 60–Z treatment. For the N:P 60+Z treatment, a significant reduction was observed in the total phytoplankton biomass and the biomass of three phytoplankton classes and three species. In Experiment III, there was an increase in the biomass of Dinophyceae with the N:P 5–Z treatment. In the N:P 5+Z treatment, there was a significant reduction in total phytoplankton biomass and the biomass of the phytoplankton class and five species. The findings of the present study reveal that zooplankton species native to a tropical reservoir can change the structure of the phytoplankton community and the response of these organisms to variations in nutrients.

Symbiotic Nitrogen Fixation by Coralloid Roots of the Cycad Macrozamia riedlei: Physiological Characteristics and Ecological Significance

1976 ◽  
Vol 3 (3) ◽  
pp. 349 ◽  
Author(s):  
J Halliday ◽  
JS Pate
Keyword(s):  
Nitrogenase Activity ◽  
Natural Habitat ◽  
Natural Populations ◽  
Molar Ratio ◽  
Fixation Rate ◽  
Plant Nitrogen ◽  
Blue Green Algae ◽  
C2h2 Reduction ◽  
Whole Plant ◽  
Coralloid Roots

'Coralloid' roots containing blue-green algae occur commonly on the upper root stocks of M. riedlei in natural habitat in Western Australia. Each coralloid mass persists for several seasons; replacement sets form at irregular intervals, especially after fire. 15N2 and acetylene reduction assays demonstrate that coralloid roots fix nitrogen at physiologically significant rates. C2H2 reduction rates by coralloid roots are higher in winter than in summer. Performance is positively correlated with rainfall; soil temperature appears to be of lesser importance. Diurnal fluctuations in nitrogenase activity occur. Calibration using 15N2 gives a molar ratio of C2H2 reduced : N2 fixed of 5.8 : 1. The seasonal average of C2H2 reduction of 14.8 nmol per g fresh wt coralloid root per min is then equivalent to 37.6 g N per kg fresh wt per year, a fixation rate potentially capable of doubling coralloid root nitrogen once in every 8 weeks, and whole plant nitrogen every 8-11 years. Returns of fixed nitrogen in two natural populations of Macrozamia are estimated by compounding measurements of biomass of host and symbiotic organs with the seasonal average for coralloid fixation rate. The values obtained (18.8 and 18.6 kg N ha-1 year-1) indicate that Macrozamia contributes significantly to the nitrogen economy of its ecosystem.

scholarly journals Revisiting Biological Nitrogen Fixation Dynamics in Soybeans

2021 ◽  
Vol 12 ◽  
Author(s):  
Ignacio A. Ciampitti ◽  
André Froes de Borja Reis ◽  
S. Carolina Córdova ◽  
Michael J. Castellano ◽  
Sotirios V. Archontoulis ◽  
...  
Keyword(s):  
Maximum Rate ◽  
Seasonal Pattern ◽  
Single Point ◽  
Clay Content ◽  
Growth Stages ◽  
N Fixation ◽  
N Budget ◽  
Fixation Rate ◽  
N Removal ◽  
Biological Nitrogen

Biological nitrogen (N) fixation is the most relevant process in soybeans (Glycine max L.) to satisfy plant N demand and sustain seed protein formation. Past studies describing N fixation for field-grown soybeans mainly focused on a single point time measurement (mainly toward the end of the season) and on the partial N budget (fixed-N minus seed N removal), overlooking the seasonal pattern of this process. Therefore, this study synthesized field datasets involving multiple temporal measurements during the crop growing season to characterize N fixation dynamics using both fixed-N (kg ha−1) and N derived from the atmosphere [Ndfa (%)] to define: (i) time to the maximum rate of N fixation (β2), (ii) time to the maximum Ndfa (α2), and (iii) the cumulative fixed-N. The main outcomes of this study are that (1) the maximum rate of N fixation was around the beginning of pod formation (R3 stage), (2) time to the maximum Ndfa (%) was after full pod formation (R4), and (3) cumulative fixation was positively associated with the seasonal vapor-pressure deficit (VPD) and growth cycle length but negatively associated with soil clay content, and (4) time to the maximum N fixation rate (β2) was positively impacted by season length and negatively impacted by high temperatures during vegetative growth (but positively for VPD, during the same period). Overall, variation in the timing of the maximum rate of N fixation occurred within a much narrower range of growth stages (R3) than the timing of the maximum Ndfa (%), which varied broadly from flowering (R1) to seed filing (R5–R6) depending on the evaluated studies. From a phenotyping standpoint, N fixation determinations after the R4 growth stage would most likely permit capturing both maximum fixed-N rate and maximum Ndfa (%). Further investigations that more closely screen the interplay between N fixation with soil-plant-environment factors should be pursued.

Anaerobic digestion of primary sludge from chemical pre-precipitation

1997 ◽  
Vol 36 (6-7) ◽  
pp. 357-365 ◽  
Author(s):  
Wouter Ghyoot ◽  
Willy Verstraete
Keyword(s):  
Anaerobic Digestion ◽  
Wastewater Treatment Plants ◽  
Oxygen Demand ◽  
Molar Ratio ◽  
Municipal Sewage ◽  
Primary Sludge ◽  
Loading Rates ◽  
Volatile Solids ◽  
Feasible Option ◽  
Kjeldahl Nitrogen

Many existing wastewater treatment plants are to be upgraded for phosphorus removal. In our study, ferric chloride was used as a coagulant in pre-precipitation of municipal sewage. Using a Fe/P molar ratio of 0.8, removal efficiencies for suspended solids (64%), chemical oxygen demand (50%), Kjeldahl nitrogen (22%), total phosphorus (43%) and orthophosphate (51%) were obtained. Anaerobic digestion of raw primary sludge yielded a volatile solids (VS) destruction of 35% at VS loading rates of 0.60 to 0.79 kg VS/m3.d. Digestion of chemically enriched primary sludge (CEP-sludge) yielded a VS destruction of 57% at a VS loading rate of 1.36 kgVS/m3.d. Comparison of the methane production per kg VS destroyed (519 to 612 1 CH4/kgVS destroyed for primary sludge, 299 to 395 1 CH4/kgVS destroyed for CEP-sludge) evidenced a change in the composition of the organic material after precipitation with coagulants; the latter sludge was enriched in less reduced compounds. The precipitated phosphorus was not released to the supernatant during anaerobic digestion. No evidence for reduced digester stability was found for digestion of CEP-sludge. These results indicate that retro-fitting a plant by chemical pre-precipitation and subsequent anaerobic digestion of the CEP-sludge is a feasible option.

scholarly journals Asymbiotic nitrogen fixation is greater in soils under long-term no-till versus conventional tillage

2018 ◽  
Author(s):  
David W. Franzen ◽  
Patrick W. Inglett ◽  
Caley K. Gasch
Keyword(s):  
Soil Microorganisms ◽  
Conventional Tillage ◽  
N Fixation ◽  
Reduction Procedure ◽  
Fixation Rate ◽  
No Till ◽  
Asymbiotic Nitrogen Fixation ◽  
Deep Sample ◽  
Similar Soil

A series of N-rate experiments was previously conducted in spring wheat, corn and sunflower in North Dakota indicated that less N was required when fields were in 6-years or more continuous no-till compared to conventional till. The objective of this study was to determine whether part of the reason for the decreased requirement for N was the greater activity of asymbiotic N-fixing organisms. Twelve paired-samplings were conducted in 2018. A surface 0-5cm deep sample was obtained in a long-term no-till field directly across the fence/road from a similar soil in conventional till. Samples were incubated in an acetylene-reduction procedure to estimate N fixation rate. Ten of twelve paired samplings had greater asymbiotic N fixation compared to the conventional till counterpart. This indicates that long-term no-till soils support greater N production from soil microorganisms than conventional till soils, which would result in lower input costs to no-till farmers.

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