Nitrogen Fixation and Phosphorus Turnover in a Hypertrophic Prairie Lake

1983 ◽  
Vol 40 (11) ◽  
pp. 1853-1860 ◽  
Author(s):  
B. G. Brownlee ◽  
T. P. Murphy
Keyword(s):  
Nitrogen Fixation ◽  
Light Intensity ◽  
Acetylene Reduction ◽  
Ammonia Volatilization ◽  
Molar Ratio ◽  
Short Term ◽  
Nitrogen Reduction ◽  
The Mean ◽  
Phosphorus Turnover

Nitrogen fixation by Aphanizomenon flos-aquae in a prairie lake in southwestern Manitoba was dependent on the light intensity and in situ oxygen concentrations. The mean molar ratio of acetylene reduction to nitrogen reduction was 5.8:1. High external ammonium concentrations did not appear to inhibit nitrogen fixation over the short term. Nitrogen fixation was not directly initiated by the bloom collapse. We propose that the coupled sequence of ammonia volatilization and nitrogen fixation was triggered by the bloom collapse and that the bloom collapse was caused by coprecipitation of orthophosphate with carbonates. 32PO4 turnover was most rapid during periods when the lake was opalescent, presumably due to carbonate precipitaton.

Nitrogen-fixing communities in an intertidal ecosystem

1978 ◽  
Vol 24 (8) ◽  
pp. 932-938 ◽  
Author(s):  
B. Ben Bohlool ◽  
William J. Wiebe
Keyword(s):  
Nitrogen Fixation ◽  
Photosynthetic Bacteria ◽  
Statistical Significance ◽  
Group Iv ◽  
Group Iii ◽  
Group I ◽  
Mud Flat ◽  
Intertidal Ecosystem ◽  
The Mean

Nitrogen fixation (acetylene reduction) associated with various communities in the intertidal sand and mud flat was measured in situ. Areas which were colonized by algae, plants, and animals generally had significantly higher activities than areas which were visibly uncolonized. The highest activities were measured at sites colonized by a mixed bloom of Oscillatoria–Euglena–photosynthetic bacteria. These areas occupied only about 1% of the surface of the sediments, yet contributed nearly 50% of the biologically fixed nitrogen. Enteromorpha communities also exhibited relatively high activities. Sites were grouped according to the statistical significance of the mean of their activities: group I: uncolonized sand, mud and gravel flats, Eelgrass (Zostera) communities, and snail (Amphibola) beds, with an estimated contribution of 1 g N ha−1 day−1; group II: Cockel (Chione) beds, 3g N ha−1 day−1; group III: Salicornia, Ulva, Juncus, and Enteromorpha, 10 g N ha−1 day−1; and group IV: Oscillatoria–Euglena–photosynthetic bacteria association, 200 g N ha−1 day−1. Enteromorpha and Oscillatoria–Euglena–photosynthetic bacteria communities showed significantly lower rates of nitrogen fixation in the dark than in the light.

scholarly journals Six years of high-precision quasi-continuous atmospheric greenhouse gas measurements at Trainou Tower (Orléans Forest, France)

2014 ◽  
Vol 7 (1) ◽  
pp. 569-604 ◽  
Author(s):  
M. Schmidt ◽  
M. Lopez ◽  
C. Yver Kwok ◽  
C. Messager ◽  
M. Ramonet ◽  
...  
Keyword(s):  
In Situ Measurements ◽  
Atmospheric Measurements ◽  
Short Term ◽  
Gas Detector ◽  
Sampling Height ◽  
The Mean ◽  
Drying System ◽  
Gas Measurements ◽  
Television Tower

Abstract. Results from the Trainou tall tower measurement station installed in 2006, are presented for atmospheric measurements of CO2, CH4, N2O, SF6, CO, H2 mole fractions and Radon-222 activity. Air is sampled from four sampling heights (180 m, 100 m, 50 m and 5 m) of the Trainou 200 m television tower in the Orléans forest in France (47°57'53'' N, 2°06'45'' E, 131 m a.s.l.). The station is equipped with a custom-build CO2 analyzer (CARIBOU), which is based on a commercial NDIR analyser (Licor 6252), and a coupled gas chromatographic GC system equipped with ECD and FID (HP6890N, Agilent) and a reduction gas detector (PP1, Peak Performer). Air intakes, pumping and air drying system are shared between the CARIBOU and the GC systems. After some initial problems, we achieved short-term repeatability (1 sigma, over several days) for the GC system of of 0.05 ppm for CO2, 1.4 ppb for CH4, 0.25 ppb for N2O, 0.08 ppb for SF6, 0.88 ppb for CO and 3.8 for H2. The repeatability of the CARIBOU CO2 analyser is 0.06 ppm. In addition to the in-situ measurements, weekly flask sampling is performed, and flask air samples are analysed at the LSCE central laboratory for the same species as well for stable isotopes of CO2. The comparison between in-situ measurements and the flask sampling showed averaged differences of 0.08 ± 1.4 ppm CO2, 0.69 ± 7.3 ppb CH4, 0.64 ± 0.62 ppb N2O, 0.01 ± 0.1 ppt SF6 and 1.5 ± 5.3 ppb CO for the years 2008–2012. At Trainou station, the mean annual increase rates from 2007 to 2011 at the 180 m sampling height were 2.2 ppm yr−1 for CO2, 4 ppb yr−1 for CH4, 0.78 ppb yr−1 for N2O and 0.29 ppt yr−1 for SF6 respectively. For all species the 180 m sampling level showed the smallest diurnal variation. Mean diurnal gradients between the 50 m and the 180 m sampling level reached up to 30 ppm CO2, 15 ppm CH4 or 0.5 ppb N2O during night whereas the mean gradients are smaller than 0.5 ppm for CO2 and 1.5 ppb for CH4 during afternoon.

Nitrogen Fixation (Acetylene Reduction) Associated with Sea Urchins (Strongylocentrotus droebachiensis) Feeding on Seaweeds and Eelgrass

1977 ◽  
Vol 34 (3) ◽  
pp. 416-420 ◽  
Author(s):  
M. L. Guerinot ◽  
W. Fong ◽  
D. G. Patriquin
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Sea Urchins ◽  
Nitrogenase Activity ◽  
Average Rate ◽  
Strongylocentrotus Droebachiensis ◽  
Molar Ratio ◽  
Laminaria Digitata ◽  
Bare Rock ◽  
Nitrogenase Activities

Sea urchins feeding in different macrophyte zones in St. Margaret's Bay, Nova Scotia, in November and December 1975 were examined for nitrogenase activity using the acetylene reduction technique. For sea urchins feeding on Laminaria digitata and L. longicruris, the average rate of acetylene reduction was equivalent to N2 fixation of 55 μg N2 per sea urchin per day assuming a 3:1 molar ratio of C2H2 reduction to N2 fixation. Lower nitrogenase activities were observed for sea urchins feeding on Agarum cribrosum and Zostera marina, and no nitrogenase activity was observed for sea urchins taken from bare rock substrate on which kelp had been absent for 4 yr. Samples of separated digestive tracts but not the degutted bodies of sea urchins exhibited nitrogenase activity, suggesting that the digestive tract is the site of nitrogen fixation in whole sea urchins.

scholarly journals Diurnal Variation in Algal Acetylene Reduction (Nitrogen Fixation) in Situ

1975 ◽  
Vol 55 (2) ◽  
pp. 273-276 ◽  
Author(s):  
Larry N. Vanderhoef ◽  
Paul J. Leibson ◽  
Robert J. Musil ◽  
Chi-Ying Huang ◽  
Robert E. Fiehweg ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Diurnal Variation ◽  
Acetylene Reduction

Seasonal and diurnal variation of nitrogenase activity (acetylene reduction) in barrel medic (Medicago truncatula Gaertn.) grown in pots

1978 ◽  
Vol 29 (5) ◽  
pp. 951 ◽  
Author(s):  
JJ Ruegg ◽  
AM Alston
Keyword(s):  
Nitrogen Fixation ◽  
Diurnal Variation ◽  
Medicago Truncatula ◽  
Acetylene Reduction ◽  
Time Course ◽  
Nitrogenase Activity ◽  
Seasonal Pattern ◽  
Molar Ratio ◽  
Multiple Use ◽  
Seasonal And Diurnal Variation

Seasonal and diurnal variation of nitrogenase activity in Medicago truncatula Gaertn. was measured by means of the acetylene reduction assay on plants grown in pots. In a glasshouse set at 20°C, the seasonal pattern of acetylene reduction (AR) activity was closely correlated with dry weight and photosynthetic area. Short-term fluctuations in AR activity were mainly associated with irradiance. Measurements made of the diurnal variation of AR activity showed that rates of AR at noon were 10–60% (average 33%) higher than the mean daily rates. Effects of defoliation and shading gave further evidence for the importance of light and recent photosynthate for nitrogen fixation in root nodules of legumes. Values for acetylene reduction integrated over time were highly correlated with the total amount of nitrogen in the plant. The molar ratio of acetylene reduced to nitrogen accumulated by the plants at the end of the experiment was 1.2 : 1. The significance of this value is discussed. Multiple use of the same plant material to study the time course of nitrogen fixation by the AR assay was found to be feasible under certain conditions.

In Situ Studies on Nitrogen Fixation with the Acetylene Reduction Technique

Science ◽  
1967 ◽  
Vol 158 (3800) ◽  
pp. 536-536 ◽  
Author(s):  
W. D. P. Stewart ◽  
G. P. Fitzgerald ◽  
R. H. Burris
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Reduction Technique ◽  
In Situ Studies

scholarly journals Use of Autologous Leucocyte- and Platelet-Rich Plasma (L-PRP) in the Treatment of Aural Hematoma in Dogs

2021 ◽  
Vol 8 (9) ◽  
pp. 172
Author(s):  
Roberta Perego ◽  
Eva Spada ◽  
Elena Moneta ◽  
Luciana Baggiani ◽  
Daniela Proverbio
Keyword(s):  
Clinical Effect ◽  
Platelet Rich Plasma ◽  
Healing Process ◽  
Short Term ◽  
Clinical Resolution ◽  
The Mean ◽  
Clinical Healing ◽  
Mean Time

Leukocyte- and platelet-rich plasma (L-PRP) can accelerate the healing process by providing increased concentrations of platelet-derived growth factors. The objective of this study was to evaluate the clinical effect of L-PRP in the treatment of canine aural hematomas associated with otitis externa. Twenty mL of citrated whole blood was collected from each of the 17 dogs included and autologous L-PRP was produced. The aural hematoma was drained and 0.5–1 mL of L-PRP was injected. The dogs were examined weekly until 7 days after complete clinical healing. A final clinical follow-up was performed 6 weeks after the first treatment with L-PRP. If there was recurrence of the aural hematoma at the first follow-up, the treatment was repeated. In total, 2/17 cases were lost after the first follow-up. In 5/17 dogs, a short-term recurrence occurred. In 12/15 cases, complete clinical resolution was achieved with a single L-PRP application (Group A1) and in 3/15 with two treatments (Group A2). The mean time to complete clinical resolution was 16 ± 8.7 days (A1) and 23.3 ± 4 days (A2), respectively. No side effects were reported. The in situ administration of autologous L-PRP resulted in a complete resolution of the aural hematoma in all dogs that completed the clinical trial.

scholarly journals The Quantitative Relationship between Nitrogen Fixation and the Acetylene-Reduction Assay

1970 ◽  
Vol 23 (4) ◽  
pp. 1015 ◽  
Author(s):  
FJ Bergersen
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Host Plants ◽  
Quantitative Relationship ◽  
Root Systems ◽  
Mean Value ◽  
Reduction Assay ◽  
Nodulated Root ◽  
The Mean ◽  
Free Media

Acetylene.reduction activity of detached soybean nodules was positively correlated with the nitrogen content of the host plants grown in nitrogen-free media. Acetylene reduction by nodulated root systems was related to light intensity preceding sampling; activity of detached nodules was lower and less influenced by light. Comparison of acetylene reduction and 15N 2 uptake by detached soybean nodules gave ratios of acetylene reduced to nitrogen fixed (C2~: NHs ratio) ranging from 2�7 to 4�2 in different experiments. The mean value for four experiments was 3�3�0�6 (S.E.). Different effects of oxygen were obtained with detached soybean nodules when 0�1 atm nitrogen and 0�1 atm acetylene were used as substrates. When the acetylene concentration was reduced to 0�005 atm the effects upon both assays were similar but the ratio of the two assays was still affected by p02.

Sediment accumulation in a series of four pilot-scale stabilization ponds

1994 ◽  
Vol 30 (8) ◽  
pp. 281-284
Author(s):  
A. Ghrabi ◽  
M. Ferchichi
Keyword(s):  
Sediment Accumulation ◽  
Pilot Scale ◽  
Sediment Depth ◽  
Short Term ◽  
Stabilization Ponds ◽  
Volatile Solids ◽  
The Mean ◽  
Depth Increase

Settling and accumulation of sediments have been measured on the bottom of the facultative and three maturation ponds of a series of pilot-scale stabilization ponds. The mean deposition rate in the facultative pond showed that the attempt to establish a short-term sedimentation by in situ measurements failed. The rates were largely overestimated and the values calculated from the sediment accumulated in a long-term are closer to the reality. The sediment depth increase rates are 5 cm/year for the facultative pond and 1.3 cm/year for second and third maturation ponds. In the last maturation pond it is 1.6 cm/year. The rate of sediments deposit (volatile solids) in the first pond can be estimated by an at−b equation.

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